I rate our 3 best wingers (Mkhi, Mata, Martial), and I'm very comfortable with Rashford as our backup 9. I think we just need a starting quality 9 like Morata or Lukaku there and we're decent up front, though lacking a proper star.
If we need to score more goals, and we do, I think we should seriously look at buying a box to box CM rather than a 6, assuming we can't get a passer like Weigl. Herrera did well as a 6 and adding a proper box to box 8 to play in front of him, next to Pogba, would give us extra juice going forward and Herrera and Lindelof would give us a good platform to move the ball from deep, rather than a normal DM who doesn't provide much playmaking or mobility.
I'd like to see us sign a 9, an 8 and an LB. I rate Shaw, but who knows how much he'll play. If Keita is the CM people seem to think he is, then this team would create too many chances for us not to score more than 54 league goals this time:
------Morata-----
Martial---Mkhitaryan
--Pogba-Keita--------
-----Herrera--------
Mendy---------Valencia
--Lindelof-Bailly------
-------De Gea--------
and then next summer we'll have only a few spots to fill, i.e a feck off star attacker like Mbappe, Bale, Griezmann, Ousmane Dembele or whoever the best attacker we can get is, with Mata or Lingard leaving, an RB to replace a 33 year old Valencia as the starter like Semedo or Henrichs (with Young or Darmian leaving), and a DM/CM to replace Carrick (retiring) and that's a proper team that shouldn't be crippled by injuries.