I think Peyton would do well to take some time off football, after his retirement.
Still, I don't know if he knows the intricacies of commanding a Football Operation. Learning how the cap works, managing people's egos, Coaching conflicts and all that. Still, I doubt anyone on the Titans or the Browns do, so he may be a good fit.
If he takes sometime to study, Manning showed he is somewhat intelligent, he could work... Still, I see him being better as an OC somewhere (Maybe he could work as a QB coach before?), he understands the playing field well