I'm always up for a dual regional game. I want to be like Ash and travel the world.
Honestly I wouldn't mind if we go back to Kanto and Johto. It would be cool if in each version you would start in a different region. Like version A you start in Kanto then in version B you start in Johto.
And yes we would need a new storyline. A new evil team or do something different with Team Rocket.