ok so wow I just quit reading half way through
Only ELITES and SPARTANS will be in multiplayer, they are being given customization options to give the game more options, however they have no special abilities....to keep the game EVEN which is why Brutes, Jackals, Hunters, Drones, and especially not grunts wont be put in, the grunts have no shields and niether do the brutes which is why brutes aren't being put in multiplayer, if you dont believe me on this go read through all of the info Bungie has released since Halo 3 was first revealed............as for campaign you only play as the chief and along side Arbie-bungie also said this, it is theorized that in Co-op one person plays as arbie
bottom line campaign chief & maybe arbiter are playable
MP only Spartan and Elite with armor vakriants playable
anything else makes game unbalanced
thehelljumpers.com
If all you want to do is complain about the game please leave.
but if you have a helpful suggestion or need help ask nicely and there will be someone to listen and help you!