SPN story concept/idea

Instead of concentrating on homework I'm trying to figure out what would happen if an Angel's "Grace" was stolen and given to Sam and Dean...if it's possible, would it change them completely? Would they go insane? And what the hell would happen to the Angel who's Grace was stuck in the body of two humans?

Also, I can't get this one vid I saw out of my head. So I downloaded the song and am listening to it way too often.