After looking through the list of 40K based games I had a flash of insight...ORK Heresy! Orks rooting out traitors to a waaaargh boss (other waaargh bosses), Bashing those who don't worship Mork by bashing 'ard nff, Attacking Chaos because it looks fun, finding gene stealer cults because they taste like chicken. Is it wrong I want this?

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Only if they don't pronounce it as 'Da Inky-Zit-Tin.'

dOrk Heresy would be hilarious.

Probably better to use Only War or Rogue Trader as a base (RT actually had full rules for Ork PCs, they weren't too crazy with a good GM, as balanced as any non-human could be in 1st ed), but I could see DH2 working with Kommandos and Weirdboyz and so forth.

But everything you said can basically be summed up as "Ork Society". Only thing I'd put a lot of effort into would be more crafting rules, for da orky kustomizations.

DH2 character creation system is a lot more flexible so I can see it would be a better fit than the stacked tier method of 1e.

First module title "The Gretchin Strike Backs!".

This has got me started on a line of thought, Slannesh Heresy, Hunting down those deamons who stay at home and read a book, write letters to the editor, play board games, and paint things in earth tones. Dark Eldar Heresy, hunting down those Dark Eldar who are Trustworthy, Loyal, Helpful, Friendly, Courteous, Kind, Obedient, Cheerful, Thrifty, Brave, Clean, and Reverent.

There are some trial rules out there for Ork based 40k roleplaying that a few GM's have done. I've seen them before, but I haven't downloaded them.

This is the famous one -->

Deffwotch https://1d4chan.org/wiki/Deffwotch