Having different chapters and sects is important but here is a bigger question. Say they do have them, how will that mesh with class advancement. Think about it this way, in cookie cutter space marine terms you start as a scout and earn brotherhood, but in the space wolves you start as a blood claw and their scouts are considered elite. Even more puzzling is how basic progression will work when there certain achievable positions that are permanent in 40k lore. For instance the dreadnought. It would be awesome to stomp around as a dreadnought, killing with heavy weapons and massive power weapons, but if you stay true to lore, once you are a dreadnought, you are always a dreadnought. You could just simply not have dreadnoughts, but then you would have to remove the other races representations of it, i.e. Ork Dreadnoughts, Chaos Dreadnoughts, and to some extent Tau Crisis Suits, Guardsmen Sentinels, and of course Eldar Wraith Guard. Having said that, I don't think vehicles will find there way into this game except in special areas or driven by NPC's. Making this game capture the lore and scope of 40k must be a challenge indeed, but I think the hardest part for the team is going to be meeting the expectations of the fans.