I've been playing Warhammer 40,000 since it was an RPG called Rogue Trader. I think would be a great direction to take the game, having the players be mercenaries or rogue traders would fit the MMO style. Archtypes like Space Marine, Eldar Aspects and Tau Castes are pretty much set in style and apperance. Not a whole lot of room for deviation and customization from "Space Marine in MK VII armor" .

I'd love to see some Jokaero, Squats and Slaan in there or least some arcane reference to made.