Well, since my thread seems to not be getting approval from the moderators, I'll suggest a feature I was planning for my own hack (which I may not be doing).
To me, it is a bit boring how you always get the same choice of starters. I know, the idea is to make sure that the Rival has an equivalent starter (usually with a type advantage), but it's just so dull. I would like to see (and was planning to make) a hack where you get your starting pokemon by playing the Safari Game, or a similar process of hunting your own down. As for the Rival (if you even need one), I say give him Evee for multiple possibilities, or Sableye and have no weakness.
Of course, really any time the game departs from the traditional formula makes it more interesting. For instance, I love hacks with branching storylines!