^^^ I think "washed up" is a poor term for some of these guys.
Perhaps it's a little too harsh, but I was using hyperbole to get people interested in looking at the thread. It might be more accurate to say "failed head coaches".
Unfortunately most new HC's go to a team that is floundering and it is difficult to turn a team around in the short window that is the current NFL. I do think they learn a lot serving as a HC, that helps them when they return to their old positions.
True, but I'm not sure it matters in this case. I want them as a coordinator, exercising the skills they have already shown. Whether they learned anything as a head coach is not relevant.
Unfortunately, most of these guys want to return to the HC position so if you bring them in you can't plan on keeping them very long.
Aren't the majority of successful coordinators looking for an opportunity as a head coach? Since many of these failed head coaches need to prove themselves again before getting another opportunity for the top job, I think we would get a number of years of valuable service from them.