He'll replace Pogba, which is fine. He's better suited to the number 10 role, and Pogba just hasn't been good enough for us. In all honesty, if we can get 150M for Pogba, and then sign Maddison and Sancho for around 170-180M combined, we'll have a net outlay for 20-30M and be a much better team.
After that we'd need a bonafide quality DM, a quality left back to supplant Shaw, and another striker for the rotation. If we ship out Matic for 10M odd, have Lukaku, Sanchez and Pogba wages off the books. I could see us investing 150M net, which after the deals mentioned above would give us 130-140M to bring in a striker, defensive midfielder, and left back. If you have Maddison as your 10, a good highly technical creative player, and McTominay as the 8 who is bringing box-to-box energy, work rate and physicality, I would want us to bring in a 6 that is in the Carrick type mould. A player whose technical and positional attributes are to the fore, rather than the physical. If we are going to continue to look to fast counters, you really need a player who can split the lines with his passing, as well as accurately switch play at a moment's notice. Basically, not a Dier or Rice. We don't need a bruiser, we need a conductor.
Personally, I feel there have to be better players than Maddison out there for the type of money we are talking. But we seem to be really hot and heavy for him. So I've kinda accepted it. On the plus side his final ball is really good, he's PL proven already, and is only 22.