Exactly - the Heisman is supposed to go to the most outstanding player that season. To try to make it an MVP award just makes it impossible to go to team that is loaded with talent.
With as much talent as USC had stockpiled, they probably could have won the same number of games with or without him in 2005. The fact that USC had other talented backs behind him and an excellent defense, shouldn't disqualify him from the Heisman.
All I have to say about 2005 is Vince Young got robbed.