I still have some Citadel Space Marine - Space Wolves (somewhere) which I painted, the warhammer side didnt appeal to me like the technologically advanced military side. The only thing with turning it into an MMO, is that space marines are meant to look identical being a Military group and the first thing in an MMO is always to customise and individualise your character. You can have any number of customisations on a Space marine but it signifies rank and fighting prowess. Unless everyone is identical (fighting under a certain banner: Space Wolves, Blood marines ect.), and then is customisable as they gain skills; I cant see how it would work.