Rashford is going to be playing as a striker this year and I hope we stop switching him around and keep him as a #9. Thats where his future is. We need two players for each position. ST - Lukaku/Rashford, LW - Martial/?, #10 - Mata/Pogba, RW - Lingard/Mkhi, CM - Fellaini/Perreira, CDM - Herrera/Carrick.
Mourinho plays with a very small rotation, and the only way Rashord will get extended minutes is as a LWF. He will occasionally play as a CF if Lukaku/Morata is absent.
I expect Lukaku+Rashford+Martial to be rotated for the CF+LWF spots.
On te other flank would like see Mata+Mkhi+new player rotating for the #10+RW spots.
Pogba will not be playing as a #10> He is not one and Mourinho ddoesnt see him as one
Paraphrasing you: the wing is better covered, as we have… no wingers! Even if Mourinho likes a extreme-forward there, the other guy should be a real winger, like Di María in Real Madrid. Of course our playmakers can play on the right, because they drift inside with Valencia entering. But we don't have much firing power there, nor proper crosses.
Di Maria was not a 'real winger' at Madrid but was more like an extra AM as he was playing on his wrong foot and drifted centrally to join Ozil.
Mourinho likes one winger to be like a WF, presenting a more direct goal threat (CR7, Pedro, Schurle etc) while the other is more like an AM (e.g Di Maria, Willian). Both are expected to drift centrally while the fullbacks will provide width. In our case, Martial/Rashford will be the WF while Mkhi will be the AM. Each are well suited to the role Mourinho usually expects.
For the #10, Mou likes a player that is an AM/trequartista with ball and a CM without it. Unfortunately there are not many such players and this might be the position that limits the team going forward. Mata is just not suited to it. so we will have to sign a very attack minded CM or a very high workrate AM. Particularly if we get Lukaku, we need someone to feed him consistently for us to get the best out of him.