Depends on when. Basically, I think he's a surefire success if he took over after Ferguson or Moyes, no way if he took over after Jose, and I'm unsure if it was after LvG or right now.
The team in 2013 had Rio, Evans, Rafael, Evra, Carrick, Nani, RvP, and Welbeck who could fit into his system, on the borderline there was Rooney, Young (as full-back), Cleverley, Kagawa. It would be curtains for Vidic, Valencia, Smalling, Jones, Fletcher, Anderson. Basically he'd be doing the type of cull LvG did.
There's a base to build from, but it would need investment in creative midfielders and wingers. KdB, Fabregas, Kroos, Thiago, Ozil, di Maria, Sanchez, Mata, and Coman moved clubs around that time, so it's possible.
Taking over after Moyes is similar except for Rio, which means additional big spend on CBs. Think this one works out too.
After LvG, eh. There's Blind, Shaw, Martial and Rashford who would make it, and Herrera, Mata, Young as the maybes. It would mean buying new first-choice, top-quality CBs, RB, CMs and a forward. Massive rebuild just after LvG's rebuild failed. Not sure if the club would allow it, though to be fair this was the summer of Pogba, Mkhi, Bailly, Zlatan.
After Jose, no. Rashford, Martial, Pogba, Shaw are in, Bailly, Herrera, and Lindelof are maybes. Needs a new right-winger, 2 more CMs, and 2-3 defenders. 3rd rebuild in 6 years, no way.
Now? Slightly better. Rashford, Fernandes, Greenwood, Pogba, Shaw, Diallo(?) and one of Maguire/Lindelof/Bailly would be in, with Martial and Cavani as maybes. Would need a new first-choice CB, CM and a RB.
I think in general the amount of spending in general is a bit exaggerated by what he has done at City. There he has infinite backup players, but he wasn't always like that - Barca won the 2009 CL final with 40-year-old Sylvinho at LB, Yaya Toure at CB, and Puyol RB.