I guess what I am saying is that I don't think Depay changing his physique will change his existing game as it doesn't look like he would amend his style to take advantage of it.
Getting back to full fitness and I think he is still an asset, Lyon played fast and had inferior versions of Auba and Dembele last year and Depay was extremely good.
But yeah, it is frustrating that Depay could be so much more with some tweaks and work here and there. Maybe Xavi could bring it out of him?
Xavi has been great with the forwards. He gives them very specific roles and has clearly improved their movement vastly.
Considering this, Memphis does have something world-class about him : chance creation. Although he sees himself as a goalscorer and protagonist, his numbers in chance creation are incredible. He nearly led Europe last season in chance creation metrics. What if Xavi could develop his role based on this?
If Xavi could teach him to play for the team and support the CF from the LW role, he can be very useful. Just as he has focused Adama and Dembele in chance creation and limited their greediness. Utilising Memphis's main strength in fashioning chances for others, and removing that greediness/lost ball proneness that infuriates people could make him valuable.
I am sure he'll find minutes anyway. Sometimes Ferran will not be the right one for the game and the tactics and Memphis will.
Side note - Memphis at United had a top speed of nearly 34km. Hard to imagine him going that fast now.