I think the question is if we need a quality midfielder or not to play in favor of shitmids like Rabiot and Arthur. I think the time to consider Fagioli as yet another primavera kid who needs to be constantly loaned out over, he's well established already and would definitely be of use for us.
We definitely need a quality midfielder, 100 percent. And yes, fully agree that Fagioli is ready for Juve. If Allegri sees him and other kids as quality players, and hence give them enough chance so that they can earn their spot and become a regular starter, that simply would be the best case.
However, if they are not good enough, or Allegri think they are, at best, rotational options, then it turns back to the question I brought forth.