How, precisely, does this prevent a team in the NBBA, say, from having 10 high quality players that they use for all of their competitive matches, and then have the coach focus entirely on three 18 year olds with very high potential?
Sounds pretty realistic to me. Let's prevent it???????
Did you notice that my suggestion still limits training effects by limiting the time/input available to a trainer? Are YOU now suggesting unlimited training?!?!?
Yes, it's realistic. It's also an abysmal decision for game balance. Right now, teams that get to the top start facing erosion because it's nearly impossible to train players at the top levels and still maintain a strong competitive roster. Teams get older, get shallower, and eventually run out of gas and move down. Remove that downward force and the game becomes much too easy for those who have a lot of money amassed and those who are already at the top.
Putting aside balance, it's also an abysmal decision for game design purposes. You are eliminating a meaningful choice that has some consequences - "Shall I train, shall I focus on training, or how shall I balance that?" and instead the default strategy becomes to train whatever you can afford and compete at your maximum ability. If there is only one right choice, there is no choice at all.
The suggestion that I'm endorsing unlimited training is patently absurd, and so I hope you got whatever laughs you wanted to get for yourself when typing it.