I really love playing history mode, so these suggestions really apply there more than anything. They could be used in regular mode if kept random though.
I’d like to see an attribute that determines how long a player stays at their peak overall. Some players hit their peak, play at that level for a couple years, and then sink back down. Some play at a high level for a good portion of their career.
To go with this peak duration, I’d want to see a progression attribute. This would determine if a player hit their peak quickly or if they take a long time to get to their best. For example, Mike Knuble was in his 30s when he was at his best. Ken Hodge Jr, hit his peak young and then fizzled.
One other thing I’dlike to see if something i can look at throughout the season that would show me who is eligible for the expansion draft. Essentially I want to have the screen where I choose who to protect and who’s contract requires them to be protected. This would allow me to plan better during the season and potentially trade a player away rather than lose him to the expansion draft. I always seem to get caught and lose a high value player because I dont know until it’s too late.