Stay:
Rashford, Antony, Garnacho, Amad, Pellistri
Bruno, Eriksen, Casemiro, Fred
Shaw, Malacia, Dalot, Wan-Bissaka, Alvaro
Lisandro, Varane, Lindelof
5 attackers, 3 mids, 4 fullbacks and 3 center backs. That's 15 players. Add 2 keepers and you're up to 17, and we need two #9s a #8, a #6, a CB and 2 keepers. That's 21 players, like say this:
----------------------------ST1(ST2)---------------------- / Rashford
Rashford(Garnacho)---------------Antony(Amad) / Pellistri
--------------------------Bruno(Eriksen)--------------- / Amad
----------------#8 (Eriksen)-------------------------------- / Fred
------------------------------Casemiro(#6)--------------- / Mainoo
Shaw(Malacia)----------------------------Dalot(Wan-Bissaka) / Alvaro
----------Lisandro(Lindelof)---Varane(RCB)------- / Shaw
----------------------------GK1(GK2)--------------------------
If we can't handle that many signings, keep De Gea (GK2), Martial (ST2) for a year and then you only need to bring in a #9, a keeper, RCB and 2 midfielders, which should be possible with fees for Sancho, Maguire, McTominay, Henderson. Tired of a giant squad of mediocre players.
9 Defenders for 4 spots, with Alvaro as 5th fullback and Shaw is the 5th CB.
Midfield is a player light but Amad and Mainoo competing to be a 6th guy is fine, they both look promising. Fred gets one last year, then we sign another #8, and Eriksen becomes full-time #10 backup.
Attack looks good with 2 strikers and Rashford as options up top, Garnacho and Amad in their right place as backup looking to improve and Pellistri works hard and has potential, 5th winger, 7th guy in attack for 3 spots feels right.