Not sure if this has been asked before, but I think it would be good if there was an U18 comp that runs along side the main comp where each team has there own squad of 15 - 18yr old players where you can develop each individual.
You can only promote a player to your main squad after the turn 18 or at seasons end.
Also if not promoted then optioned to be put on reserves list or into market for recruiter points.
I think training should be more position specific and rewarding so managers see results upon promoting.
Give the players no star rating until promoted and make these teams do guild challenges with no fan base or star ratings or mb then it's a true strategy game and guild vs guild

It's a very popular idea and I like some of what you say. Look in the news and patch notes most recent topic if you want other suggestions and thoughts. Hopefully some others add some more ideas here too, always fun to think of better ways to do things.