This one concerns me. Makes me feel that CMC had others turn it down and he did not have any other options at this point. I would think the CMC would now be very involved on the offensive side of the ball now, but not sure if that would be a good move either.
The head coach should have good expertise on one side of the ball and with CMC it should be offense, so he can help bring Manning along. When I've seen video of CMC when he was at Toledo he had what looked like a playbook hanging from his belt, so maybe he stays involved with the offense anyway. Not that unusual for a head coach to be actively involved on the side of the ball where he has his expertise.