I think a good example of how to gradually develop and integrate young, promising players into the first team squad can be found in how Guardiola has handled Foden. Pep clearly rates him, and began by using him in brief cameo appearances in the final minutes of games, to now where the player is seeing significantly more game time- even starting in certain situations. Thus, Foden is being gradually integrated into the first XI, given time to get acclimated to his role in the team, and to the EPL.
It is therefore harsh and unfair to young guys like Middleton, who get pitched as a starter into Rangers games - often with a great deal at stake - and are expected to perform. If Rangers - but any team really - are serious about developing a viable youth academy, it seems to me that a strategy has to be found that allows for the gradual integration of 'elite prospects' into the first team squad, otherwise what's the point of it all?