yeah unique ideas all based off COD4

anyway, imperial guard could be based on COD4, but I would Eldar like crysis, because they actually have suits that adapt, Space Marines more like in the Halo direction, because they can just absorb damage.
Tyranids should have a real nasty close combat attack, and make them fast.
Orks are supposed to be slow, but with some kind of special ability that they can't shoot, but will move faster.
Chaos marines just like marines, but with a ability to choose which god you can worship, and adjust strengths and weaknesses accordingly.
grey knights should be slow, tough, and choppy in close combat.
sister of battle can be medium speed, not really tough, but can shoot real good, and can choose to increase rate of fire, or strengths of shots, accuracy etc etc.
tau can be slow, and really shooty, with a long range, and good accuracy and strength, just not a lot of shots.
necrons should be the real damage takers in the game, all that they can really do is bite bullets.
for dark eldar it would be real nice to have a fast movement, and maybe a drug ability
that's all I can think of right now, this is just what I think would be the a awesome game.
maybe do PVP multiplayer just like normal, all characters the same statistics, and do a gametype where a few players are pushed into a dungeon where they have to team up to try and get to the end, and all the characters are different.