I would like to see Nick Diaz ref a match between Jake Shield and Mayhem. I don't see how anything could go wrong there. Any others?
Shonie Carter would always be welcome, put a wireless mic on him and see what he says about the fight while it's going on.
Actually, if they can't (or choose not to) set up Shamrock or Miletich v. Royce Gracie when they go to Brazil, I think it would be interesting to see him ref.
Oh, how about Ken as a ref for Tito's next match.