Although they have fought already I think Marquardt and Damien would be good coaches. Wouldn't be very much shit talking but they both have very good people they could bring in to help the new meat and either guy would be a great influence on an up and comer. These two guys would be most beneficial to the fighters imo.
Bisping and Sonnen would be great for the back and forth banter but Chael will probably want to stay out of the public eye for a while at least.
If anyone needs some positive exposure on weekly tv it would be Bisping. Like many fans, I liked Bisping before he coached on TUF and maybe he can spin some peoples perception of him if he acts less like an ass.