I suggest "Individual Training" as a complement to current training.
It would work just like ordinary training(trainer, height, age and elastic effect), but with a much lower effect, like 5-10%? of ordinary training dosage(based on selection of training). Other training restriction apply, like cap hit but they are not bound to playing minutes or positions. This is not meant to give every player 2 extra pops every season, but a bonus pop every now and then.
This way you could try to get a players Stamina or Free Throws up a level over a couple of seasons without having to train the whole team a week or two every season. Or any other Skill for that matter. All forms of training is available, individual or team, except game shape.
It's also more realistic, that players actually learn something even if the don't play on the training position that week.
A player who is recieving ordinary training will focus 100% on that, but if he doesn't get 48+min training, he will recieve (up to 100% total training) his individual training.
Lets say Player A trains Shot Blocking but only gets 47min on the C position this week, he gets his ordinary training and that's calculated to, lets say, roughly 97% of ordinary training, that means there's space for 3% of the individual training.
Player B how only gets 20min on the C position gets his normal amount of individual training 5-10%.
Players will develop(very slowly) even if they don't recieve any (ordinary) training and it should be easier to develop lower skills than higher. Maybe there should be a ceiling on how high this individual training actually works.
Since your TO:s usually don't get individual training and the training dosage is so small, there will still be need for Team Training like Stamina and Free Throws to raise these skills on your team.