I'm going with the Imperial Guard and Sisters of Battle. I got a few friends who like the Guard so it woudl be fun to fight alongside them and slaughter them. Likewise it woudl be nice too see some female players getting to play as the holy sisters. The Sisters of Battle are just as bad ass as their Astarties brothers.
tau better be able to use kroot when they are released...as well as both pathfinders and fire warriors(or this could be a single class?), and all stealth suit models.
Fire Warriors and Pathfinders as one class and just depending on loadout? mh.... idk..... Perhaps, depends on how it will in generally turn out because then you could make also Tactical and Assault Marine separate and just make it depending on jetpack or no jetpack xD
but pathfinders aren't differentiated by something as key as a jetpack, stealth suit, or teleporter. really all that separates them is their weapon--and if you do that for tau, you dont need to do it for marines. granted, i would REALLY prefer they did a no class system--instead, you pick gear from gear you have unlocked, and using some things locks off other things--for example, if you pick a jump pack, then you can't use heavy weapons or regular weapons. what do u think about that--kinda want to start a thread about it...