Firstly, forget any stories about UEFA bringing in allocations and restrictions. Even if they had the balls to move against the interests of their most powerful members it is hardly an appropriate time to do it with the game in its present formation still bringing in vast amounts of cash.
It is not unlikely that any such rule would contravene EU laws by restricting the clubs right to employ and a players right to be employed..The days have long gone when sports ruling bodies could do as they liked.
Also true that very few youth kids come through any clubs training and reach the standard required for a Prem side. Most move away after years of training down to lesser leagues. The football world is full of such kids.
At present prices it is a bonus if a club can get one or two home made players through the kids team and up to top standard, but to expect any more than that or the foundation of a Prem side is a pipe dream. Any rule of the type suggested would have Pool out there with all the others , cheque book in hand.
LC