I don't know about that, honestly. Fabregas is the last ridiculously young player I can remember in central midfield at a club in England legitimately expected to challenge for the league with all the pressures and stresses that brings even for unprepared (mentally) players with bags of experience and international caps.
Ole has had more room to experiment this season due to how things have panned out, but from the get go, next, we'll be playing for the title and the point tallies needed don't allow much margin for error or blooding of youngsters unless they're insanely talented and/or of certain constitution (mental fortititude). Is that fair on Bellingham? He's in relative nowheresville at the moment not playing for anything much; perhaps a playoff place, but even that's not expected.
He could obviously come here and take to the game and the league like a duck to water, but, at 16-17, if he doesn't, it shouldn't be a mark against him, but we're not going to entertain growing pains if we're not getting those crucial points on the board - from any youngster, not even Bellingham, per se.
A great scenario would be that we have a strong midfield with a solid rotation that allows for a nurtured player to come in without the standard slipping. Pogba (I'll assume he stays), Fernandes, Fred, McTominay, Partey (as an example), Matic (in his resurgent form) and Bellingham, would comfortably be one of the best midfield units in the league, but then, game time for all of them would be the challenge, wouldn't it?