Forgive me if this has been stated, as I can't possibly read all of these posts.  I think it would be cool if I could expand the major league team's roster in September to 40 players.   
 
Also, I've noticed some stats errors.  I played through one full season and noticed that minor league players retained, and added to, stats from the previous season.  I had a couple guys with 80 home runs and that's downright silly.