Suggestion:
Increase frequency of retiring players - > coaches/managers. (low)
Add in first and third base coaches (low)
Increase the number of coaches allowed per team, and make it flexible, like say Football Managerm, ie: "General coaches" (Low, may be a silly idea.)
Fix the "loopholes" in contracts, ie: 10mil a year plus 20mil for starting a game. That way the owner approves it, and the player accepts it. It's cheating.
(Medium/High)