When i thing abaout WH40KIM loads of possibility jump at me :). Do you have any future goals to make othr factions and races playable? Like abigger star maps, orks invade from this side, chaos from that, someone inviteted the Necrons over and the Eldar put theire noses in the mix as well. All Factions work theire way to an ancient System in the middle of the mix where you can play 4vs4 pvp for objectives and honor and... stuiff like this ^^. Or play the PvE part in a carebare manner in your more or less secure space where you bully rebels arround and purge a little chaos here and there.
Most Races in WH40K would be "easy" to implement in a 3 class system as well but you could play all the fluff of WH40K that way. First of thats maybe to big, to much and you dont have bought the license for al of that stuff but do you have some dreams, i talk about about dreams for the game no promises, regarding the future of WH40KIM?