Because there was some talks and speculation for stamina training and affect on the game, here is my suggestion for stamina.
We managers hate to give up training for stamina (and also free throws in the past). So i have 2 suggestions adressing this problem:
-make some sort of a training complex to train stamina on its own (just like free throws)
-let the stamina level increase if a player plays a lot of games/minutes and decrease if a player plays very few games.
I like the first one better, but the second one is not far behind it. Whatever you would choose, the weekly increase should be little, because stamina only has 9 levels. But (positive) changes should be made in this field.
Regards