You can't replace a squad in a full window. It doesn't work like that. It would sink a team but as a squad and in terms of motivation for any one in the club and looking at the club. Financially it would be a huge burden. He brought in four specialist last year, Bailly, Ibra, Mihki and Pogba. A good chunk of the squad, but ones that need time to develop in. They're there now. Now he'll replace another 4 maybe 5 if someone is leaving. But it's yet again a gradual turn over. It's the natural way to do it.
My problems start with his tactics and will grow when he chucks DDG, Shaw, Darmian and probably Martial out of the squad. All 4 are good enough to be a part of the starting eleven if given the chance. But he refuses to. Instead we'll keep wasteful players like Valencia, Fellaini, Lingard and Jones.