Significantly more than the fact that old leaders didn't age, I'm upset by the lack of E4 in the world tournament. Including Koga who I guess got the boot because he was promoted. Seems weird there's like Volkner, but no Flint. Doesn't seem like it could've been too difficult to maneuver.
On top of that, the stat trainers and Fronteir Brains would have been nice. They obviously didn't really care about trying to maintain a continuity with it because there's no aging, so it would've been great if they just threw in as many named characters as possible. Most of these trainers have DS sprites already so it wouldn't be too much work. They're renowned trainers, so giving them some more exposure would have been great.