New armour system.

[Avianmosquito]

If it were just that, it wouldn't be all that bad. The issue is that there are just so many things to keep track of; you have different armor values for each body part, and 3 different layers of potential armor.

If you are changing armour frequently enough that this is at all a concern, there is something wrong with you.

This brings up another few implications; how do you determine which body part got hit? Do you have to use called shots for everything, or do you create a new attack system entirely?

You CHOOSE targets, some are harder to hit than others. I figured that would be obvious.

Also, this much data is all well and good for PCs; you have people with a vested interest in their gear, but how does this work for large groups of enemies?

Enemies use generic pre-built armour sets.

Are you going to track the state of the armor on each of the 25 Hobgoblin raiders your party is fighting?

This isn't D&D. I should not have to say that when it says that in the title of the thread. You will not have a body count of 9001 by the end of your campaign, and a single encounter will never throw dozens of NPCs at you, ever. If you got into a fight with 25 hobgoblins, you would be dead too fast to care about their armour because being massively outnumbered plays out pretty realistically in this game.

This game is designed for small parties, ideally with two players. If there's only three enemies, tracking their armour is not bad.

The game also focuses a LOT on boss fights with 1-2 enemies, even when you have more than two players. If there is only one enemy, tracking its armour is nothing.

Further, item condition is an optional rule and is never applied to NPCs, so only plates and barriers ever actually need to be tracked.

That starts to approach near Dwarf-Fortress levels of bookkeeping, since you have to track the injury level of each body part and each of the three layers of armor on every combatant.

Yes, every one of the like four combatants. I don't see a problem.

Again, if this was all in the background, this could work, but since you have to write down each and every change for everyone, this starts to become just too much to keep track of.

I think you are really just making a lot of assumptions that you need to reconsider before coming to such a conclusion.

In addition, using a DR based armor system really punishes people like the Monk or the Rogue, people who try to avoid damage by not getting hit in the first place rather than letting their armor absorb the blow.

There are no classes.

If there is no incentive for a dodge based class, the "meta" per say is going to turn into a bunch of people strapping on the heaviest armor they can carry and bashing each other with weapons that do the most damage. To be fair, that's probably the most realistic option, but I feel that it would tend to stunt varied and innovative gameplay.

Not really. The fact that it is so easy to circumvent armour in-game without using armour that is impractically heavy makes lighter options viable, and the fact that this isn't D&D and you will not be in combat all (or even most) of the time makes light options even more viable.

Movement and stamina are really important in this system, especially in combat, and encumbrance impacts both of these things. Heavier armour means moving slower (even losing movement modes) and recovering stamina slower (possibly not at all or even losing it over time), and that can get you killed. Stealth is also a valuable asset and encumbrance messes that right up. The goal when making a custom armour set is to get as much protection as you need, where you need it, in as little weight and with as little money as possible, and different builds have different capabilities and different needs so their ideals will all be different as well.