You have my support.
A player that is being trained and get minutes improves upon his potential and age, even if not as drastically as a player who get personal training.
Training and game time keeps a player in game-shape regardless, but that has nothing to do with the improvement part that is parallel to the game-shape issue.
Would it affect the game? Yes of course and by definition.
Would it make the game worse? Not at all. It will make training and training desicions a bigger part of the game at the expense of the "eBay" part.