"How about we don't kill them and take their stuff?"

[Arbane]

At this point you might as well just play Mutants and Masterminds.

Definitely a change from D&D - superheroes generally don't kill people and take their stuff, aside from the Punisher. (They may do one or the other, depending on subgenre, but usually not both.)

The hard part is getting all the players on the same page as to what SORT of superheroes they are supposed to be, so you don't get a team of Mary Marvel, Ben Grimm, Promethea, Deadpool and BLOODWULF THE EVISCERATOR.

Or worse, 5 Moody Loners.

[Yora]

I think even more important than rules is establishing "Who is your PC and what does he do?" To give the players references from fiction as to by what logic characters set goals and make plans, interact with NPCs and react to danger. The Treasure Hunter and Monster Slayer for Hire ("monsters/bandits threaten our village/city/kingdom, please get rid of them for us") are well established and need no introduction or pointers. As GM you merely have to point at a dungeon and say "there is your target, go get it". Ideally a bit more elaborate, but it's obvious what the PCs are trying to accomplish.

There are a few other archetypes in RPGs, but I find it challenging to translate them into high fantasy environments that come with certain expectations how society works.

I think translating Call of Cthulhu should probably be quite straightforward. With a setting that is more medieval and does not have large numbers of big scary monsters roaming around, the absense of powerful heroes is logical and it makes sense for civilians to go after hidden supernatural threats. One could even play a captain of the guard or a priest, if you can get across that this is not a setting in which every priest casts lots of spells and veteran warriors routinely kill ogres and manticores. The power level of Middle Earth should be a great match for that.

If I understand it right (maybe not), the setup assumed by Apocaypse World is centered around one or a few small settlements in a lawless frontier plagued by violent gangs and a permanent scarcity of resources. The job of the players is simply to stay alive despite the danger and chaos around them, and perhaps to find ways to prosper and rise above the misery. (It's a strange rulebook and doesn't outright say so, but I think that's what's assumed.)
This also translates easily enough to any world where there is no government in control and villages are under threat by scarcity, bandits, and strange things coming from the wildeness. Players should grasp easily enough what kind of people they are playing and what they will be doing.
One example of attempting to emulate the fiction of such a game (though actually being completely linear and scripted) is Dragon Age II. This is a game set in a world with elves, dwarves, dragons, wizards, undead, and demons, but the story is about a noname who arrives with nothing in a city whose government is failing and where madmen and fanatics are taking over the street. And over the course of several years the party works to expose and break up these threats to the peace and the hero rises to become a popular community leader. Now the combat system consists of killing dozens and hundreds of faceless bandits over and over and emptying endless numbers of barrels and chests standing around everywhere. But when you take away this senseless padding and look just at the plot, the behavior of the characters does match.
It also should work perfectly in a Dark Sun campaign. Though obviously this one was designed to be the postapocalyptic version of a generic D&D world.

[NichG]

I tend to run campaigns where the ultimate goals end up being about changing fundamental aspects of what it means to exist in some form or other. In the fantasy context, these tend to correspond to fictional stories about the industrial revolution (e.g. 'we had this stereotypical fantasy kingdom, but then someone introduced sanitation, the printing press, mass production, automation, and modern medicine - what does the transition look like?'). But it could also be mythological things like the sorts of stories about how the seasons came to be. I've had arcs of campaigns such as 'The embodiment of Death died, and the other gods are still busy looking for a replacement. What are you guys going to do about it?' or 'Conservation of detail is a real in-setting phenomenon and as a natural resource it's being stretched thin by growing populations and elaborate multiverse type settings, go do something about it.' or 'The powers of Fate got a little overzealous and now causality has been inverted: it is now the future which determines the past. You're the people who were alive during the moment the flip happened, the last beings in the universe with real agency, as both directions of time are both future and past to you. Go meddle in your own timeline to create the world you want to see.'

That said, I have difficulty figuring out how to scale this stuff down. If I specify cosmic, impossible problems and then let the players have cosmic, impossible powers, then there's a tension that sustains the game in the form of the 'what would we need to solve this obviously impossible thing (and how do we get it, and are we willing to live in a world where its a thing)?' puzzle. That tension replaces the usual 'are we going to win?' tension of a combat or other sort of overt adversarial conflict. For smaller scale things, I don't feel like I have as many options to use which still have interesting moments of agency. A lot of the person-scale fiction that isn't about conflict ends up being about perseverance under adversity, which doesn't convert well to a game format.

I do tend to like heists and mysteries for the smaller scale, but they both require a bit too much prep in order to make them the bread and butter of an entire campaign.

[Yora]

My lofty vision is a campaign in which people avoid the unexplored wilderness because they know that its the home of strange and dangerous spirits that are really the masters of the world. But when the PCs get there, they realize they had not even the slightest clue how strange and dangerous the vast majority of the world really is, and how small the familiar safety of their homelands.

The best approach I can think of is to instruct the players to create characters who think "There is something out there in the trees beyond the river. And it worries me."

One option is to go full out unplanned storygame sandbox as is suggested in Apocalypse World and just riff off whatever crazy theories the players chatter about during play. But that has me really afraid of it all ending up like X-Files or Lost with everything getting swamped in an incomprehensible and inconsistent mess. Though on the other hand, you can never come up in advance with something as compelling as what the players conjecture while rilling each other up in panic.

[Filraen]

I'm really enjoying running a Curse of Strahd 5e campaign right now, with a group of mostly new players who are much more invested in storylines than they are in killing things. I've pegged leveling up to milestones rather than XP or combat encounters... which is great because they've talked their way out of or ran away from every single potential combat encounter save two really easy random ones. I also have a strong bent towards collaborative storytelling so this works well for all involved. Sure, they're probably going to have an epic battle at the very end (if they survive) but it'll be all the more satisfying for everything they're going to learn about the land, its people, and their parts in it.

I tend to incentivize non-combat solutions and make social interplay interesting by calling on checks regularly when they are trying to do something where failure will make a difference in outcome. ("Please make a persuasion check to mollify the baron who caught you sneaking into his mansion.") However, if they're just trying to do something where they could do it over and over again enough to succeed, and success or failure won't make a difference in the outcome, then I tend to just narrate what they did and not have people rolling unnecessarily all the time. (Strategy props to the Angry GM blog.)

I realize this can strike some as over-lenient with regards to the rules, but like I said, my players are more invested in the storytelling and character-playing aspects, which seems to be within your interest as well. I would echo the above in that it can depend on who you're playing with. But also, letting players know or dropping obvious hints that combat is... not the best way to solve things. (Like making their kills have severe consequences. Oh, that goblin horde you wiped out two sessions ago? Great, now you've triggered full-scale raids on the nearby villages. Why does this sound familiar... don't mind me, just finished re-reading "Why the Paladin Got His Scar".)

I like your lofty vision. That sounds like something that might be a lot of fun if you're okay improvising a lot. In my experience, stories can come together surprisingly well even if you don't plan things out beforehand. I may or may not be a Nanowrimo veteran.

[Koo Rehtorb]

I'm really enjoying running a Curse of Strahd 5e campaign right now, with a group of mostly new players who are much more invested in storylines than they are in killing things. I've pegged leveling up to milestones rather than XP or combat encounters... which is great because they've talked their way out of or ran away from every single potential combat encounter save two really easy random ones. I also have a strong bent towards collaborative storytelling so this works well for all involved. Sure, they're probably going to have an epic battle at the very end (if they survive) but it'll be all the more satisfying for everything they're going to learn about the land, its people, and their parts in it.

I tend to incentivize non-combat solutions and make social interplay interesting by calling on checks regularly when they are trying to do something where failure will make a difference in outcome. ("Please make a persuasion check to mollify the baron who caught you sneaking into his mansion.") However, if they're just trying to do something where they could do it over and over again enough to succeed, and success or failure won't make a difference in the outcome, then I tend to just narrate what they did and not have people rolling unnecessarily all the time. (Strategy props to the Angry GM blog.)

Might I suggest trying a system that actively supports what you're doing here instead of fighting you on it? D&D in general, and 3-5e in particular, are designed for fighting things.

[Mordar]

Since you've mentioned Pendragon, and are clearly at least open to the idea of reshaping Call of C'thulhu...there is something that might provide another middle ground option.

The Stormbringer/Elric game from (initially) Chaosium and later Mongoose offers a much less Murderhobo style game against the backdrop of an established world (though probably not familiar to many players, especially the sub-40 year old set) that is rife with political opportunity and still uncivilized enough to provide for exploration. The system - particularly the chaosium version - lends itself to improvement by means other than stabbing goblins in the head...but your more combat-seeking players can still have enough fighting to be entertained.

- M

[PhoenixPhyre]

Honestly, the only combat/loot focused people I've played with have been the grognards. All the new players have been focused on making a mark on the world. And that's playing bog-standard 5e D&D.

It's much more about the culture of the table in my experience rather than the exact rule system.

I tend to incentivize non-combat solutions and make social interplay interesting by calling on checks regularly when they are trying to do something where failure will make a difference in outcome. ("Please make a persuasion check to mollify the baron who caught you sneaking into his mansion.") However, if they're just trying to do something where they could do it over and over again enough to succeed, and success or failure won't make a difference in the outcome, then I tend to just narrate what they did and not have people rolling unnecessarily all the time. (Strategy props to the Angry GM blog.)

This isn't just an Angry GM thing--this is the exact advice in the 5e DMG. Checks are supposed to only be called for things where

a) there's a decent chance of failure (but it's not guaranteed)
b) failure is interesting

The DM is supposed to tread the middle ground between "roll for everything" and "roll to persuade the DM"-style whim-based decision-making.

[SimonMoon6]

TORG was an interesting game system that really pushed for the "cinematic" play style.

However, it is fairly heavily tied into its particular setting.

[Zombimode]

Which is where I think that the system really matters. D&D is based on the core premise of "defeat enemy, gain XP, get advancement". This doesn't really lend itself to a campaign where the story takes two or three year long breaks on a regular basis.

I have no idea how you can reach this conclusion.

"defeat enemy overcame challenge, gain XP, get advancement" is an underlying structure for the game Portion of the RPG package. The first to parts are not even neccesary for D&D, as "you Level up when the GM says so" is a workable method.
Sure, overcoming challanges and getting some kind of advancement influence the type of stories that emerge during play. It does not however prevent the roleplay of actual characters (instead of gamepieces) or sophisticated stories or settings.

If you think that changing System or modifying Systems will (by itself) lead to a more mature roleplaying experience, you are deluding yourself.

The system matters very, very little. It is just a description layer. Ist influence is dwarfed by:
- the conceptual layer of both a) the Setting, and b) the narrative, which includes the GMs ability to execute their ideas
- the willingnes and ability of the Players interact with their own character, other Players characters, the Setting and the narrative. This is influence by the Players interrest in any of these.

All of this is independent of the description layer.

System is important, but it matters (only) a the preferencial layer. If you don't like interacting through the interface provided by the System, the quality of your roleplaying will be decreased. Same for the reverse.


If you still think that, lets say D&D (any Edition/the Edition you are mostly concerned with), somehow prevents mature characters/settings/naratives, take any CRPG that would fit your idea of a good PnP experience (taking the differences of the media into account, of course). Then ask yourself if switching the gamesystem to something else would Change anything about the characters, the Setting or the narrative.


The reason why I argue so vehemently against the notion of "D&D is a bad System for more mature themes, characters and Settings" is that it simply does not match my experience with D&D and other system in the last 14 years.

[gkathellar]

Take a look at Legends of the Wulin. It's unusual in that it wants to replicate the narrative and poetic aspects of wuxia, rather than just having people do a lot of flips, so it gets ... weird (bonus points for being a Jenna Moran game).

For example, when you successfully attack someone, rather than doing damage, you cause "ripples." Ripples can describe physical wounds, but also things like spiritual imbalances and emotional turmoil, and the whole system of resolving them gets incredibly ad-hoc and bizarre.

I'm not necessarily recommending LotW as a game, to be clear, although it is very cool, but it's worth looking at just for the sheer strangeness of its ideas, given that it's a game built around an action subgenre.

[Yora]

The Stormbringer/Elric game from (initially) Chaosium and later Mongoose offers a much less Murderhobo style game against the backdrop of an established world (though probably not familiar to many players, especially the sub-40 year old set) that is rife with political opportunity and still uncivilized enough to provide for exploration.

TORG was an interesting game system that really pushed for the "cinematic" play style.

Take a look at Legends of the Wulin. It's unusual in that it wants to replicate the narrative and poetic aspects of wuxia, rather than just having people do a lot of flips, so it gets ... weird

Please share with us what type of characters player play in the game, what they commonly do, and how the system gives them incentives to play in its specific style.

[Koo Rehtorb]

The reason why I argue so vehemently against the notion of "D&D is a bad System for more mature themes, characters and Settings" is that it simply does not match my experience with D&D and other system in the last 14 years.

You can roleplay in anything. That doesn't make it a good system to facilitate such. You could roleplay in Monopoly if you want to, and if everyone is dedicated and committed to it then it might even be good roleplay. That doesn't mean you probably wouldn't have an easier and better time roleplaying in something that actually supports it.

[gkathellar]

Blades in the Dark is another very non-murderhobo system. Shut Up & Sit Down has a good review/write up of it here.

Please share with us what type of characters player play in the game, what they commonly do, and how the system gives them incentives to play in its specific style.

Sure. Legends of the Wulin is a mid-magic wuxia game that gets pretty heavily into Chinese folklore and cosmology (including, semi-notoriously, a bit of weird Taoist sex magic) without ever really involving gods or immortals or whatever.

The game mostly eschews attributes or combat-specific stats in favor of abilities granted by kung-fu, special equipment, one's personal virtues (including socially acceptable virtues like honor and also "dark virtues," like individualism because this is trying to be authentic), and a line-up of positive and negative conditions (which include things like hyperactive chi, physical wounds, emotional conflict, etc). A lot of focus goes into description as a source of mechanics - for instance, every set of physical techniques (an "external style") loses its bonuses against certain types of attack and defense, encouraging the opponent to try to determine those weaknesses and seek them out. There's no HP system at all, and instead, attacks cause ripples which then cause certain penalizing conditions - or just Defeat Means Frienship!

All characters with stats are reasonably skilled kung-fu practitioners, but PCs also have a class (Warrior, Doctor, Priest, Courtier, or Scholar) which grants them access to various "secret arts" related to their profession. Everyone starts with one external and one internal style, the latter of which you develop to learn cool moves from. As you learn more and stronger kung fu, your chi gets stronger, which includes normal chi, various types of elemental chi required to power elemental kung fu, "corrupt" chi that's super-versatile but EVIL, and enlightened chi, which is really expensive but the strongest chi of all. There's a very loose leveling system built around a point-system, in which one's overall power, or rank, is determined by total "destiny" accumulated, and that destiny is in turn spent on particular things, including skills, kung fu, more secrets arts, and "lore sheets."

Lore sheets are basically packages of in-character knowledge and connections to the world bought piecemeal or as a whole - for example, the "Heavenly Sword Society" lore sheet might provide knowledge of secret kung fu, organizational clout with the society, apprenticeship with a famous sword master, ownership (provisional or permanent) of one of the society's famous blades, or access to a special virtue. Other lore sheets might include institutions like "the Imperial Army," religious affiliations like "Taoism," or "Buddhism," or initiation into secret knowledge.

LotW is not a well-organized system, and it has a few problems, but it's also really interesting for just how heavily it leans on its genre for mechanical inspiration, rather than the old RPG standbys. It also stresses true hearts and loyalty and shouting a lot about true hearts and loyalty, so, you know, I like that.

[SimonMoon6]

Re: TORG

Please share with us what type of characters player play in the game, what they commonly do, and how the system gives them incentives to play in its specific style.

Describing TORG? This could take a while.

The kinds of characters that play in the game? Lots of different types.

It's best to describe the setting first. It is modern day (well back in the 1980s or 1990s) Earth. Then, some invaders from other universes arrive. As they do so, they overwrite our reality with their reality. In North America, the invaders are from a primitive dinosaur-based world. In England, the invaders are from a generic fantasy world. In Egypt, the invaders are from a "pulp heroes" world. In Japan, the invaders are from a "generic Japanese stuff" world. In Indonesia, the invaders are from a horror world. In France, the invaders are from an evil religious world that got co-opted by a cyberpunk world, creating an invading force of religious cyberpunk characters, led by the "Cyberpope".

Some people of Earth are rewritten by the local invading forces, becoming like characters from those worlds. The PCs are heroes who can resist changes in their reality. The PCs might be people from Earth, they might be people from Earth who were changed by the invading forces, or they might be good guys from those invading worlds who are here to help.

The overall goal of the PCs is to kick out the invaders. That's easier said than done, not just because the invaders are powerful and have huge armies. They can overwrite our reality through planting certain items called "stelae". When three stelae form a triangle, the invading reality's rules come rushing into the land inside the triangle. So, the PCs want to pull up the stelae and remove them, but there's a catch: that would cause the original reality to rush back, but if a person has their reality changed twice in this way (once by the invaders, once by kicking out the invaders), then they DIE. They just die. So, pure brute force won't work (even if the stelae can be found, which is another area of difficulty). However, people who have heard the great stories of the victories of the PCs can regain some of their own reality safely, so one goal of the PCs is to accomplish great goals and then tell everyone about it (and, yes, there are game mechanics for all of this).

But that's all long term goal stuff. In the short term, the PCs are trying to stop whatever current evil plans the badguys might be up to. (This is your "what they commonly do".) That might involve espionage, searching for clues, or talking to local magistrates. But, of course, there's also fighting because, you know, it is a role-playing game. Still, the use of non-combat skills is often just as important (or more) as combat, and the rules even try to make the use of such skills during an encounter dramatically interesting. Most "important" skill checks (like disarming a bomb before it goes off) will have four parts to success, generically labelled parts A, B, C, and D, but specific skill checks would have specific results for each part (like A: open the bomb case, B: decide which wire to cut, C: cut the wire... that sort of thing). Then, the deck of cards that comes with the game will allow you to try each part at different parts of the encounter (though you can try something that the deck doesn't allow, with a penalty).

A big part of the game is using the kinds of skills that we might think of as Charisma-based skill during combat. Maybe you try to "trick" the opponent in combat ("look over there!", "He's the impostor, not me", etc.). That's just one of many such skills you might use. The deck makes this a big part of combat, as each round, you will get a bonus when using a certain one of those skills and, if you're already good at such a skill, you often might as well try. These sorts of checks can have a variety of impacts on combat, usually small but often worthwhile.

I hope that's answered enough of your questions. I could go on forever...

[Mordar]

Please share with us what type of characters player play in the game, what they commonly do, and how the system gives them incentives to play in its specific style.

Characters: Very low magic "fantasy" characters (can you say low magic and fantasy together?). Priests and wizard types are EXTREMELY rare, even for PCs. Fafhrd and the Grey Mouser would fit well here (even though they had wizardly patrons) as would Marco Polo, Sinbad, the Dread Pirate Roberts, Aragorn and Jason (of the Argonauts, not of the Friday the 13ths). From a personal perspective, I liked my traveling merchant and alchemist (more herbalist) characters.

What they do: Stormbringer supports standard fRPG play with the notable caveat that healing is not at D&D levels, so groups need to take care to not have the 4 big encounters per game day mentality. It also better supports (in my opinion) investigative, exploratory, and social play from a mechanical perspective. You can spend your game days searching for rare herbs for a special potion that will make you wealthy (while your erstwhile friend and bodyguard helps you), and you can arrange and manage a trade expedition across the sea. Yup, you'll probably find brigands, pirates, monsters and spies in the way of your goals, so you'll have to fight them too.

Yes, you can do all those things in all games. But Stormbringer (like Call of C'thulhu) uses a broad skill system that can encourage diversity in non-combat skills and rewards that diversity by its methodology of improvement. Instead of a system built on the idea of garnering EXP by offing opponents and taking their stuff (which, yes, you can handwave away or embrace the "obstacles" rules) and leveling up to new spells, feats and abilities, Stormbringer is a non-level based game where you improve the things you work on improving within the game. You get better at Bargain by bargaining, Performing by performing, and Club by clubbing, if you will. Furthermore, all the skills are handled in the same fashion, and while combat does get special attention, it is not at the same disproportionate level as say D&D.

Combined with the more limited ability to absorb damage/magic it away and earth-shattering PC spells flying about by level 5, the non-level nature and skill-based system do not encourage murderhobo or dungeon grind game play. In effect, it takes away the traditional drive to kill and loot as the dominating path to improvement and puts it on much more equal footing with other motivations. Thus it takes a lot less shoe-horning to make a mercantile game, or a political intrigue game, work in Stormbringer than it does in some other games. But you can still play a cool elemental gods vs. demons vs. Chaos gods game if you want to!

tl;dr: There are no levels, skill treatment and granularity allow non-combat skills to shine equally brightly, and limited magic limits chain-combat potential. Thus non-combat play isn't disincentivized.

- M

[Arbane]

Stormbringer is _low_ fantasy?

Player characters can be demon-summoning sorcerers right out of the gate, the gods take a (semi-)active interest in what PCs are up to, the whole world is locked in a titanic struggle between Law and Chaos (Moorcock's works are one place Gygax nicked that from, the other is Poul Anderson) and travelling to alternate dimensions is possible, if not commonplace.

[Mordar]

Stormbringer is _low_ fantasy?

Player characters can be demon-summoning sorcerers right out of the gate, the gods take a (semi-)active interest in what PCs are up to, the whole world is locked in a titanic struggle between Law and Chaos (Moorcock's works are one place Gygax nicked that from, the other is Poul Anderson) and travelling to alternate dimensions is possible, if not commonplace.

That's why I struggled with the naming convention. There is very potent magic in the world, but it isn't commonplace. There aren't magic shops selling scrolls and potions of miraculous things. You won't find a suit of +2 Chain Mail in a dungeon ready to wear, and your characters aren't shooting lightning bolts or curing grievous injuries with a touch. You could make your game more magical...allowing greater choice in profession, skewing attributes...but even then, it still isn't the same as a D&D Wizard/Cleric.

Yes, you could be able to summon some elementals out of the gate, but they are not great powers (initially), and certainly not with any great frequency. Properly following character creation methodology the chances of being a Priest/Sorcerer capable of such feats is about as likely as having Psionics in AD&D, perhaps slightly better. Sure, they put the "summoning" skill on the character sheet...but none of the characters in the two games I played got to use it.

As far as the Gods and dimension hopping (and even the whole priest/sorcerer thing) is concerned, if you use the tables to determine place of origin, those mostly only matter if you were one of the 5% of characters that were Melnibonean or Pan Tangian. Most of the Young Kingdom types didn't have to worry about such things. Maybe 10% of the non-Melnibonean/Pan Tangers were nobles or priests, and to be able to summon you still needed a pretty good Int and Pow. As far as the Godly struggles go...well, sure, but they seldom touch the lives of normal mortals. It is akin to playing Call of C'thulhu during the Great War or WWII...it forms the backdrop and perhaps influences stories, but your characters aren't intended to face the Kaiser or have tea with Mussolini.

- M

[Cluedrew]

The reason why I argue so vehemently against the notion of "D&D is a bad System for more mature themes, characters and Settings" is that it simply does not match my experience with D&D and other system in the last 14 years.

My early role-playing experience was freeform, take turns saying stuff and pretty much the only rule is to keep things consistent. I'm not sure what you mean by "mature" (you could have given it a E for Everyone rating) but we told lots of stories about character interactions, politics, "phycology", hacking and report cards. You don't really need support to do these things, you can do them on your own.

In fact D&D's attempts to provide support for these things have been such that I have seen arguments that it is impossible for a system to do better than simply get out of the way and let people free-form. (From people who had played other systems as well, so it isn't just D&D.) D&D basically has three systems in it: combat, spell casting and everything else. The everything else system is stretched rather thin. Of course if you find that it does do enough, I would like to hear about it. I'm really into system design and different perspectives are great.

I do agree with your other point though, system alone isn't going to make a change. But I think it could help.

[Friv]

The system matters very, very little. It is just a description layer. Ist influence is dwarfed by:
- the conceptual layer of both a) the Setting, and b) the narrative, which includes the GMs ability to execute their ideas
- the willingnes and ability of the Players interact with their own character, other Players characters, the Setting and the narrative. This is influence by the Players interrest in any of these.

All of this is independent of the description layer.

How familiar are you with newer RPGs, especially those outside the largest publishers? There are a vast array of games out there for whom the system and setting are interwoven to the degree that they are effectively impossible to pull apart without substantial houseruling. A good system should support a desired style of play, and provide backing for the narratives that it suggests.

D&D provides a very specific system that supports a fairly specific playstyle. Just because you can use it for other styles doesn't mean that it does them as well as a game designed for them.

[GunDragon]

I’ve always wanted to run play D&D in a modern setting with superhero characters to cure setting boredom. Mechanically I feel 3.5 can handle it with the following rules:

1. Your character must have a theme that fits with a modern superhero setting’s world. Spells, feats, etc need DM signoff. For the most part.
2. There will be dangerous amounts of homebrew involved which may or may get retconned in and out as we go
3. If you want to use your superpower (typically at level 1 you get a castX/day version of a spell or actionable ability of some sort as a freebie, with more uses as you level) in a different way to RAW, generally it’ll be a DC15 roll to learn how to do that if there is no other way to do it that can’t be reflavoured. Improvisation on the fly would be interesting.
4. Where fantasy based rules is incompatible or insufficient, we will kludge rules from guesstimations off mechanics and approximate ‘lets try this’ness

My main worry is that it would become slow to translate the game on the fly into a different one, plus it might limit players too much

I tried running a game like that using Pathfinder a couple of times. On both accounts, it was an absolute disaster.

[NichG]

How familiar are you with newer RPGs, especially those outside the largest publishers? There are a vast array of games out there for whom the system and setting are interwoven to the degree that they are effectively impossible to pull apart without substantial houseruling. A good system should support a desired style of play, and provide backing for the narratives that it suggests.

D&D provides a very specific system that supports a fairly specific playstyle. Just because you can use it for other styles doesn't mean that it does them as well as a game designed for them.

D&D has a sort of hierarchical structure and diversity of hooks that honestly I rarely see in concept-systems which try to express a certain genre. A lot of those concept games end up falling on the side of being too general or too specific. D&D, perhaps because of its incoherent development history, seems often to fail more gracefully when homebrew is factored in.

E.g. to add bureaucratic power struggles over the fate of humanity to Last Stand, a game about fighting Kaiju, I'd have to graft on a totally disconnected subsystem from scratch that interprets throwaway fluff statements about battle powers and decides which if any should transfer to human interaction. To add a kingdom management element or a logistics puzzle to Fate I'm going to end up fighting the 'everything is an Aspect' design philosophy which is otherwise uniformly applied.

With D&D, the game structure can sort of be fine-grained or coarse-grained conditionally, and abilities sort of work across levels. E.g. I can still figure out how much Wall of Stone helps someone construct a palace even if it wasn't really made for that purpose. So if I make a subsystem about disaster management in typhoons and tsunamis, there's still stuff in the base system that connects despite not being designed for it.

I don't think it's impossible for concept games to have that property, but it doesn't seem to be something that most niche designers explicitly try to achieve.