I think it'd be great for him to be under Mata's wing for a lot of the season. Physically he'll have the same issues, but he can learn a lot from him to deal with it, while I think Gomes has more natural explosiveness and is a bit more aggressive than Mata which will help him. Would be criminal to not give him chances though, loads of talent. His play style is also very possession oriented while being very creative, so being the most advanced of a midfield 3 could suit him perfectly and really help in terms of dominating possession.
Like a future team of:
Martial Rashford Greenwood
Gomes Pogba
McTominay/Longstaff
Shaw Lindelof Maguire Wan Bissaka
De Gea/Henderson
Maybe a bit too idealistic/dreaming and hoping everyone works out, but assuming players stay at the club and progress, style wise, it looks very well balanced.