Players can watch video, games etc.. For most the regimens they need minutes in an actual game. so having improvements in any skill is realistic.
What is unrealistic is....
Any player not designated to improve by the GM doesn't improve....
If real world GMs could make a player improve...man I'm sure they'd be happy. As it turns out though players really develop as a matter of their own commitment and the coaches would work on every players. Some guys end up like Darius Miles, very few like Michael Jordan and most somwhere inbetween.
To me realistic GM control on training would be getting better trainers to improve the overall rate of improvement and to choose coaches/trainers which focus on certain skills, causing a higher rate of improvement in those skills (usually goes hand in hand with the primary offensive/defensive tactic of said coaches)....
All players should improve constantly, but at different rates and as is currently set up, all players should also see drops in skill. That would be realistic....
I agree with this.
I just thought of it right now, (this looks like for suggestion thread forums but I'm not sure if it is a good suggestion). Instead of the 10% cross training, split the 10% to all the players in the roster. That way, every player will constantly improve but at a very slow rate.
So training will look like 90% a set of players, depending on the manager's choice. Then around 10/15 %= 0.67% random training to all the other players which may or may not include the player that receives the 90%. Of course that number can be changed.