A long list of possibilities, but who would be mad enough to accept this challenge. Over the last 6 years the club Manchester United has hired and fired 5 if you include Ryan Giggs (caretaker) and Ole Gunnar Solskjaer who hasn't been fired yet and still has his job. How long though as it can't be long.
The problem is the expectations are just too high for a club with a dismal squad. The managers since Ferguson's departure haven't been given the time required to turn around the clubs fortunes on the field. If they are honest with themselves this is a 3-5 year plan and if they had just stuck with one of them who knows where they would be right now.
Mourinhio wasn't a bad manager and didn't become a bad manager overnight as his track record speaks for itself. Unfortunately he is a manger who can add to a team and improve it, but I don't think they, Van Gall and the others realised how bad things were there. The team needs rebuilding from scratch with the exception of a few youngsters. Adding one or two big names every year has made the fans happy ,but the team has become weaker.
Looking at the list of candidates no one stands out in my opinion who could take on this mammoth task and come out the other side successful. Maybe Allegri as he really wants this position and has been waiting on hold for nearly 1 year now according to reports.
What Rodgers has done at Leicester has attracted attention, but then Leicester wasn't a bad team and needed direction. They one the premiership title a short while ago and the core of that team is still there. Pochettino I can see going to Real Madrid at some point and I believe that is where he will end up so he won't take on this position when it comes available.
United like to add a name and maybe will jump for the likes of Zinedine Zidane who may be able to lure bigger named players to the club. Whatever manager they decide on needs to be able to attract players as the current team and it's position in the league is not a selling point. The club is going to have to overpay for players as that is the reality of their situation. Players move as they want to further their careers by winning titles and trophies and nothing is coming to Old Trafford anytime soon.