Well, I wanted to make an Italian translation of this game since I was a kid, so being able to change the NPC text would be something I'd like to do.
Also, I didn't know Android 18 was planned to be a playable character, kinda weird since her role in the Buu Saga wasn't that important to beign with, but hey, I remember (when I used to mess around with Action Replay on this game on YT almost 13 years ago) that Videl also was able to throw Ki Blasts full with unused sprite animation, and many other NPC characters were fully playable without crashing the game or glitching out (until you go in the World Map at least), and that was weird.
Also point 4 would be cool for messing around and creating some cool custom challenges, something like fighting more bosses (or all of them?) at once.