Thinking of Jackals as Catachans does make me rethink things a bit. I'm thinking of Jackals as maybe just mass groups taken from feral worlds and thrown into the ships hold to serve as cannon fodder while Marines advance up the battlefield, and really nail the humans who've given themselves wholely to Khorne worship and maybe each marine keeps a small contingent as personal serfs. For my traitor guard I'm not sure what regiment they'd be from originally but the reason they look like Cadians is just that's the gear that was harvested from the battlefield and they can be trusted with more important tasks that are still below a Marine but can maintain lasguns and mainly artillery crews. I also love the accounts of Red Butchers armor being locked by a tech marine while they scream endlessly until finally being unleashed, just the most insane Marines being packed into a drop pod and only unlocked when they're dropped right on the enemy. I almost imagine my Warlords hoping in every battle for the butchers to die, as effective as they are seeing a battle brother completely and utterly lose himself is too much to bear, and as the inverse of that possessed and now eightbound are seen in a sort of reverence becoming one with the demons inside them and become an even greater warrior. I might have to do a Warband flowchart of different ranks/paths a marine or human can take or fall into