If we're being so for real.... I know they *mentioned* stage show. And that could mean anything, I guess. But this should stay a 3D show VERY similar to how Muppet*Vision 3D was..
It seems so simple.. Have Pete Doctor work with his team to come up with a great 3D show with Mike and Sulley. He is great with story treatments-adding humor and heart.
Have Roz be an AA that is in the balcony where Waldorf and Statler sat, interacting with the characters on screen throughout. On the other balcony (where Bean is) have a Boo AA.
And have maybe George as a costumed character coming out during the show, with hilarious gags of shouting "2319!" because he's around all us humans.