Not sure if I already stuck this here, but the ability to re-play missions and / or chapters after you get the 100%. Just go to the list, pick what you want, and re-play.
While I do like the stats board (it's fun to read), there could be a few other things put on it.
Removing the Arcace games could free up some space for other things, nobody seems to like them that much anyway.
And fix the damn Merry-Go-Round already. I was highly pissed off that it would never operate.