Warhammer 40K Tabletop XIV: "Pray for 6's!"

[Renegade Paladin]

If you want pure pinning, then psyker battle squads and sniper rifles/mortars all around. You'd want a company command squad, not a primaris psyker, because the command squad can take pinning weapons and give orders, and the psyker actually contributes nothing to pinning. You could also take storm troopers with the Behind Enemy Lines ability, but that only works the first time they fire, so if you want consistent pinning, Ratlings are better (and cheaper)

If you want a viable list with a pinning element, then you use ordnance barrage vehicles with a psyker battle squad or two in Chimeras. I'll pound out a couple real quick here, but keep in mind that I don't play these lists and can't give practical advice; I just know how Guard works.

1000 points:

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Company command squad - 90
-4 sniper rifles
-Camo cloaks

Psyker battle squad - 80
-2 additional psykers

Psyker battle squad - 80
-2 additional psykers

Ratling squad - 70
-4 additional ratlings

Infantry platoon - 285
-Platoon command squad
--2 sniper rifles, mortar team
-Infantry squad
--sniper rifle, mortar team
-Infantry squad
--sniper rifle, mortar team
-Infantry squad
--sniper rifle, mortar team
-Heavy weapons squad

Veteran squad - 90
-3 sniper rifles, mortar team

Veteran squad - 90
-3 sniper rifles, mortar team

Colossus siege mortar - 140

Griffon heavy mortar - 75

Major problem: Nothing in the list is over S6. Mech is king. You lose, barring your opponent being an all-infantry list. On the bright side, everything pins. If you're willing to overlook the Basilisk's high minimum barrage range (and remember that it doesn't have a no direct fire rule, so you can still shoot at things closer than that if you don't barrage), you could drop the Colossus, Griffon, and 35 points from somewhere (likely the command squad's camo cloaks, a ratling, and a sniper rifle from one of the blob squads, since they're less efficient on BS3) and get two Basilisks, which still pin things far away and can blast tanks better than a lascannon, barrage or no.

To expand to 1500, I'd keep the above and add 500 points of serious anti-armor, probably a lascannon blob and some tanks, possibly a Medusa with bastion breacher shells, and give the psykers Chimeras. It isn't more pinning (remember the Medusa is direct fire, and thus doesn't force pinning checks despite being part of an ordnance battery), but it shores up the major weakness of the list.

Edit:

Well I wasn't really planning on using said homebrew in a low level game anyway. I've actually found something I could use for space marine armor, that being the magitech templar, but was curious as to if there was any homebrew specifically put out as a conversion or could be easily refluffed like the aforementioned magitech templar.

Just to throw this out there, when my group insisted on running a BESM d20 campaign, I protested by building a Space Marine rather than their stupid anime nonsense. I just took some levels of Mecha Pilot and applied the mech rules to power armor instead of a giant robot, and proceeded to take all the handy traits that closely mimic a Space Marine's extra organ functions.