My biggest concern for him won't be his ability to call plays or design an offense. He's proven he can do that. My concern is how well he will do as a leader of men and managing the game.
That's fair, but that's pretty much so the concern for every HC you hire unless they were a successful HC in the NFL at a previous stop. And you don't really get that option very often. Even loud outgoing guys like Rizzi and Campbell aren't guaranteed to be good leaders in the long run.