I think John Morrison. When he was on Smackdown he put on some of the best matches and even made some main events and got a World Title Shot. He added alot to the show.
Sheamus was WWE champion, you can't have a WWE champion mid-carder.Defitantly Morrison, he could easily thrive on Smackdown, Sheamus would as well with feuds with Taker Mysterio Big Show and Edge to put him over even more, same with Barrett
Sheamus was WWE champion, you can't have a WWE champion mid-carder.
^To this I say that Swagger is credible enough to be in the M.E, he's just a very low M.E.
On topic, anyone to be moved from Raw to Smackdown would have to be a face. There are already so many SD midcard heels that it'd have to be someone like R-Truth, John Morrison, or maybe Evan Bourne or Mark Henry.