For me it's in 3 tiers:
Tier 1 - CB and RW
CB
I don't see a clear starting CB ready to carry Maguire, Lindelof or Bailly next year. Ideally we're talking about a left-footed defensive leader, but really the main concern is a proper CB who can defend, run and pass.
RW
Diallo should be the backup RW next year and James should be Rashford's backup at LW. Need a starter here. If we sign Grealish as our big signing instead of Haaland or Sancho, I think Rashford at RW or basically Mason at RWF with Rash up top and Grealish and Bruno behind them in more of a 4-2-2-2 is fine too.
Tier 2 - Striker, DM
Striker
Greenwood is 21 in 89 for us, largely playing out wide, looks more comfortable in the buildup as a 9 and clearly has the skill to link play (and unlike Martial the desire to then get into the box after) and will be 20 early into next season. If Cavani or Martial is here to allow him to blood into the team you could argue that's not really going to be a hole by Xmas.
And against a high line, I'd be fine with Rashford as the 9, though James or Pogba (if he's around) on the left might not be up to it at LW so he might be needed there.
DM
If Pogba stays, I could easily see him or VDB having a nice season or combining to have one as our 8, with Fred and McTominay doing the job at the 6 as their more defensive partner.
Tier 3 - RWB
We need an attacking player who can give Wan-Bissaka a rest and maybe play ahead of him when we got 3 at the back and need a wing-back there, and come on with 20 to go when we're attacking. Lamptey really does make perfect sense here for us and for them, and it's not like we couldn't send them a loanee that would immediately help them, like Brandon Williams, Laird or Diogo Dalot to replace him, or Pellistri or Tuanzebe.
This is lower because I could see one of the 3 RBs mentioned above taking the role and also it's a backup role and Wan-Bissaka is doing fine playing 90% of the minutes anyways if healthy, even if ideally he's closer to 65-70 with a better attacking player around 30-35.