I just thought of something, especially while thinking about how you could make it so that only Imperium was playable. Basically it's like where in WAR, they are saying that the play experience is different for each race. In WoW, the play experience is different only in fighting style. But even then, they are split into archetypes. So only the archetypes are different and the classes for each race just look different.
But in WAR, how you do things is different for each race. And the same thing can be done for 40KO. Each race not only looks different, but has a different form of military, economic, political, and social organization.
Each race has different disadvantages and advantages, or maybe the same but of different intensities, for doing things the incorrect and correct ways respectively. And each race has different required parameters to gain individuality and independence for the player character. The Imperium has the most opportunities for players to grab individuality and independence. Whereas other races don't have as many of those opportunities, but they would still be freakin' fun to play. And they can still have some or all of the systems of ranking to show how much a player has progressed; including rank, reputation, prestige, assets, money, gear, and level.
It's the best MMORPG business model