for me I would want a customizable character definitely. and you can buy clothes and stuff and change if seasons change and if you ride a Pokemon on a water route, you have a swimsuit. stuff like that. I would also like to say bye to HMs. They are the most annoying things ever. I think 2 regions like GSC is a great idea. It really makes the game longer too.
My big dream for a game is to have like an RPG type thing where you play connected to the internet on a console or computer and visit all regions. and if they release new Pokemon, you can download an update for the game so you can catch them and go to new places. and you don't have to wait forever for events and everything. Much like the game idea found at the link in my signature. I've modified the idea, so some stuff there has changed.