I'm already thinking for MLB 16 as baseball is almost over and below are a few things I would like to see added to Diamond Dynasty.
Ability to complete different collections to unlock diamond players.
Weekly challenges where you play the hottest team on that week.
Ability to play the team of the week or month with the players that perform the best on that week/month.
Release various version of player cards. ex if a non name player goes 4-4 with 3HR, release a diamond version of that player.
Ability to sell cards back to SDS instead of having X amount of copies of that specific card.
Add more legends throughout the year, example, Chipper Jones, David Justice, Sammy Sosa, Ken Griffey Jr, Pedro Martinez, etc.