I get where you are coming from Newy, but for me Karanka and McLaren were both assistants when those teams and their managers were at the peak, the top table of their domestic leagues and in Europe too. Carrick is maybe more just his timing of being there, but the same level these days would be a Klopp / Guardiola assistant maybe? Carrick just isn't at the level of the other three IMO.
The fact that they were captains or are from the north east doesn't mean much to me really, you'd think Carrick has lived away from the area most of his life, going to West Ham in his teens and settling in the north west. Lets be honest, the chances of him being here more than two years seems pretty slim these days anyway. I just think there will be better candidates. Especially if he does favour 4-1-4-1. We are heavy with strikers and centre halves, and have no DM in the squad and no cover at LB.
That said, he may have good contacts in the Man U development squads and be able to strengthen us with good youth players.