I think it would be better if it were a U-18 approach. Player age limits would be between 15 minimum to 17 at the oldest and once they turn 18 you have to make the decision to officially call them up to the main team or dump them. The earliest they could play for you main team is 18 so they have to stay in the youth squad regardless of what age you got them.
Training being limited to a level 3 trainer max at that point would make sense because they would still be developing but before the age of 18 which is the minimum age for the regular teams now anyway. Once they are on the main squad, they can be trained like anyone else.
Furthermore and MOST Importantly...this wouldn't be supporter specific. This would be for all players and it would be optional. If you don't want a Youth academy for your organization, you wouldn't have to have one. It would be similar to your Utopia team just more limited in regards to the following:
Age of players (15-17 Call up or drop date being their 18th birthday or just before it)
Staff acquisition (You'd only be able to hire a trainer between levels 1 to 3 and a Scout which wouldn't have a level which would make the finding of youth players equally random regardless of what division you play in or how much money you have. Team doctor and other staff would be whoever you have hired to your Senior team)
Arena (would be your Senior team arena. They would play before or on different days from your Senior team)
A maximum of 4 players could be called up at once. It wouldn't make sense for any team to have all 15 year olds or all 17 year olds. Once selecting the option of starting a youth team, youd be given 4 players aged 15, 16, and 17 for a full initial squad of 12 players that you can scout players throughout the season and add for a roster of up to 15 players max.(or 18)
Youth academies are a well noted part of the soccer world but they can be applied to the basketball world as well.
A huge benefit from this would be more playable content to retain both long time and brand new players to the game.
This could also help in developing a Buzzer Beater community with a higher content of well rounded players.
Finally, to make this truly accessible to all players and not just the mega rich in D.1 or D.2, make the price of starting a youth academy something reasonable like say $200,000 with a $10,000 weekly upkeep fee. The main and only additional thing you really need for youth teams is a place for them to play, the players themselves (many parents would actually pay to have their kids have an opportunity to play for a youth academy and have a shot at the pros), and a trainer/coach for them. Of course you can always go more in depth than that but for development and simplicities sake, it could be kept at that which would make it doable for anyone. Even a broke team if they save up over a season could eventually get involved in the youth game.
Because of an introduction of the U-18 Youth system, the current draft could honestly be kept just as it is, or you could reduce it from 3 rounds to 2 rounds. Either way, This adds another positive element to the game. Hattrick, a soccer manager game does something similar to this already and I think its wildly successful there. I sincerely believe it would be here too. Id rather have that than the mobile app but if this doesn't come until after wards that's fine too.
Fun fact...I didn't like Hattrick at first. I almost dropped it the same day I started it. It was the element of having a Youth Academy that kept me around and now I actually like the game. I like BB far more though so why shouldn't the BB world have something equally awesome that would benefit everyone?