Grealish, above all. Ticks every box, other than affordability.
Pedro Neto - with his development curve, speed, skills, style of play and evident confidence, I think there's a lot to say for him as a potential United player. Wouldn't be cheap, but I would be surprised if his value doesn't increase significantly over the next couple of seasons. Not what we need positionally speaking, though.
Raphinha - would be a terrific fit for the right wing, definitely has the talent.
Mateus Pereira - Looks to me like a player who might really take off on a more talented team. Has some positional versatility too.
Tariq Lamptey - the way he's dominated at Brighton tells of a special talent, and he'd be an intriguing alternative option to AWB at RB, offerig very different things.
Martin Ødegaard - has shown at Arsenal he can elevate a team, and the positional fit is a good one, since he can play both as a no 10 and on Right wing. Probably as a no 8 too, though that would be to waste much of his potential.