I've had a good think about this and I assume he wants to play 4231 next season, his preferred 433.
For this system we currently lack (including depth):
-2 Box-to-box midfielders
-Rightback
-Left winger (assuming Di Maria/Januzaj compete for the right)
-Right centreback
-Depth for LCB/LB
Memphis Depay is a no brainer for me, I've pretty much seen all his matches since they've been broadcasted including his youth matches. He's a perfect fit imo.
Rightback is probably Clyne/Danillo. Not sure what his plans are with McNair and Valencia but Rafael probably is leaving.
Box-to-box players are a hard to find commodity and I think he wanted Strootman after this season. His new setback (removing scar tissue from the first operation which succeeded) means he's back only just before preseason. Not sure if we'll go for him, but we sure as hell are going for someone like him. We won't buy 2 of these type of players since they're expensive. The 2nd midfielder will probably be a player who can cover for CDM and BTB.
A good right centreback to replace one of Jones/Smalling. Marquinhos/Hummels, or someone who's good in ball possesion.
Maybe Evans will be replaced with another multifunctional LCB/LB to cover for Rojo and Shaw, probably won't be a first team player. Depends on Blackett.
So for the positions:
GK: De Gea, Valdes
RB: Clyne, Valencia, McNair
RCB: Hummels, Smalling, McNair
LCB: Rojo, new backup1, Blackett
LB: Shaw, new backup1, Rojo, Blind
CDM: Blind, Carrick, new backup2
BTB: a Strootman type, new backup2
CAM: Herrera, Fellaini, Rooney
LW: Memphis, Young, Lingard
RW: Di Maria, Januzaj, Valencia
ST: Rooney, RvP, Wilson
Leaving:
Hernandez, Falcao, Cleverly, Lindegaard, Nani, Jones, Evans, Rafael, Mata