Since Ryan Diem started out his career at guard, I was wondering why he couldn't end his career there also. Clearly he doesn't have the same quickness as before needed to play tackle but I think he is probably still strong enough to play at guard.
Starting line up with diem at guard would be like this IMO:
LT LG C RG RT
Castonzo Ijalana Saturday Diem Johnson
I'm surprised this idea hasn't floated around that much.