Actually, someone has beat you to it! In the Q&A forum under "what to do with an old trainer", there's pics of a trainer with wings reversed. Fake ailerons marked on wings, and looks like new elevators put on other side of "foreplanes". Also, looks like he's made an all-flying rudder/fin from the pics. Flies apparently!
I LOVE this idea - might buy a cheap ARTF trainer just to try it on.
Cam