I always thought it might be an interesting idea to always have a slot open for an X-Man. I would have Iron Man make an overture to Beast to return. He turns it down but recommends:
Cyclops. I would like to see how he would fit into the Cap/leadership role, especially now that Cap seems to be leaving. His first task (even though I love him on the team) would be to fire Wolverine (after he smacks him around a little first, of course.)
When he leaves, I would like to see Colossus and Kitty leave the x-mansion and get some respectability. They need to get out of there and grow a little.
Of non-x (and as-yet-to-be-resurrected) characters; Well, Ben Reilly was never an Avenger was he?