My very favorite idea is the old-school bowls +1 game if there remain 2 undefeated teams. Even if that means there are 3 undefeateds after the bowls and it becomes a beauty contest.
If no undefeated teams remain, it's a beauty contest anyway. Don't like it? Don't lose.
In such a system, Miami and Washington would have played in '91. Michigan and Nebraska in '97. Auburn vs USC in '04.