Iceman seems like such a natural fit, I'm surprised he's never been on the team.
I liked seeing Sunfire on the Unity Team, but I'd want to see him on a regular Avengers roster where he can gain prominence and a little more development. He's been straddling the line between jerk and likable jerk for some time and an Avengers run might solidify his character, especially since his personality was conceived during a very different and at this point, outdated political environment.
Also, Storm (for a lineup that doesn't have Thor)