If we play 3-5-2 more often then I don't think we need to make anymore buys, maybe like 1 or 2 max.
Forwards: We would have Sane, Sterling, Aguero and Jesus. Even if Aguero is phased out that leaves 3 for 2 spots. I think this is better anyways because Sane and Sterling both thrive when they are more central. Bernardo can play up here as well.
Midfield: 2x Silvas, Kevin, Gundogan and Dinho is probably good cover for the midfield 3, maybe another defensive midfielder to phase out Fernandinho (Fabinho please), and that's it.
Defense: Mendy and Delph LWB, Maffeo and Danilo RWB. Back 3 of: Kompany, Otamendi, Stones, Laporte, and Walker. Walker can also play RWB.
Walker's versatility to play RCB and RWB means I don't think another CB needs to be bought. I think Delph can do the business as a LWB, we've never seen him try to go wide and cross, I think he can add that weapon to his game.
So at most I see a defensive midfielder needing to be bought and that's it. Foden and Diaz as backups should be seen as an option as well.