Great way to build a team is to buy & bed in together a new spine - i.e. a GK, CB, CM & ST
Can it be done in one window? Possibly, IF they can work some magic and get shut of a few of those overpaid underperformers. Unfortunately, I think that a Garnacho or Mainoo might need to be sold to help the process as we see little or zero interest whatsoever in anybody taking Casemiro. If Antony and Marcus Rashford can show enough whilst out on loan, perhaps the coffers will swell beyond what is due from Sancho.
Gyökeres is way too good for the league he is in, he runs every defender ragged and I have little doubt he would fail in the PL. His movement, pace, strength, balance and finishing are at a level way beyond anything currently at United. Ruben Amorim knows him better than anyone, I just hope he makes it happen.
In the middle, I would say if money is available, Ederson. He might prove costly but he has what it takes and like Gyökeres, at 26 is in his prime years and should remain so for a nice four or five year span.
CB is looking promising for the future with the additions of Yoro and Heaven. Experience from Harry and de Ligt in the squad will help but the issue now, given his latest bad luck, is the Martinez injuries are starting to pile up. Personally, I like the look of another Sporting Lisbon player that Amorim knows all too well, Ousmane Diomande. He is comfortable on the ball, strong, fast and a good tackler. Furthermore, he is only 21. There is a reported release clause of around 70 million, which may well be a stumbling block.
Andrij Lunin looks a fine young keeper but he has recently extended his contract with Real Madrid. Given time, perhaps one of either Vitek or Harrison, the two talented prospects already at the club, could step into the role - if the defenders in front of them are up to the task, it might help!