I like the idea of maybe having eldar and dark eldar corsairs and ork pirates fucking with our fleets and being a pain as npc's. But I feel like this game would be better served by having all of the players on the same team. Playing Imperial navy or space marine strike fleets. that would keep up maximum interaction between the players and not encourage anyone to be off doing their own thing in the corner. 

And races like Tau and tyranids should obviously be left out because they make no sense in the context of the twelfth black crusade. I only add that because I guarantee if this makes it to an OOC page. Someone is going to drop in and ask to play some lone ranger tau admiral who inexplicably managed to get his fleet half a galaxy away from where the tau empire is. 

Because player characters.......