Release all the hidden attribute info on a player as soon as he retires. Let us see all unrealized maxings, what his training efficiency rate was, etc. etc. Then we'll be able to decipher a lot more about what YTC really means, if we'll never be given any other insights.
This would not affect gameplay or balance but would heighten a manager's length in the game and invaluable feedback so managers can get better at their craft and enjoy the game more. (And stick around, and want to maybe spend money on the game.)