I honestly think that is the worst job in the NFL right now. You have a lot of guaranteed money tied up with a small, heavily declining, aging QB. It will handcuff you as the head coach for years. By the time they can move on from the QB, you as the head coach will be out the door. If Quinn was an offensive minded coach and thought that he could scene or fix things on the offensive end, then yeah, go for it. However, as a defensive coach, you are relying on others to fix things on offense.
I think it is a no win for him or at the very least, very long odds to succeed.