Sounds like a lot of effort and palava just to get some kids to grow. I'd buy up all the 5 star wonderkids the wallet can manage, then loan out the ones who don't quite make the initial cut for rotation who are old enough, the much younger kids of course in the youth setup; and then if any don't reach their proper potential and fall short by some way sell them off. Chances are if you get a huge huge crop of sensational players and manage to keep them all through the odd game and loaning them out then you'll have a squad who simply can't be beaten some years down the line. Might kill the game for challenge and fun, but the trophy haul will be legendary.