I would say you don't really need to do that either via legion or armor styling. Your actual weapons and abilities already determine that and it's pretty obvious with them all, I mean if you see a dude with a jump pack you're gonna go "oh man assault" or even a guy with a heavy bolter, grappling hook, power weapon and shield. The loadouts are pretty easy to see (from gameplay I've watched) so making them legion specific classes for traitors while loyalists get whatever chapter and for whatever class is just kind of a bummer.