Con: The Vrabel and John Schneider dynamic
Until getting fired in Tennessee, there were rumors that Mike Vrabel could leave coaching and become a general manager elsewhere. His name was definitely bandied about by people who follow the Patriots as a potential replacement for Bill Belichick not as coach but as general manager. Vrabel is a smart guy and he is a coach who seemingly wants a bit more power.
According to Dianna Russini of the Athletic, Vrabel and the general manager with the Titans, Ran Carthon, did not see eye-to-eye on roster decisions. Vrabel wanted full control over who should be on the roster and Carthon disagreed. That is Carthon's right as GM, of course, as he should oversee who is signed as a free agent and have input on the team's draft. Thinking Vrabel was not OK with the situation with the Titans yet being OK with the same situation with the Seahawks seems like a foolish thought.
I have no doubt that Mike Vrabel would have a good idea about who should be on an NFL roster and who should not be. He was a successful player on many successful New England Patriots' teams. But a head coach not being OK with the general manager having input on roster decisions is just wrong.
Mike Vrabel should not even be thought of as a possibility to replace Pete Carroll in Seattle because Carroll and John Schneider had an excellent working relationship, one that is rare in the NFL. Now Schneider has more power with Carroll gone. There is no way Schneider is going to back away from his newfound power simply so Seattle can hire Vrabel.