I think other regions beyond what we have would seperate us from other groups, and I don't mean custom ones (which, actually, I dislike, but there we go xP). I saw that Orre's been suggested before and shot down, but I'll suggest it again, because... People power! I'd also like to suggest the Orange Islands, which is my favourite.
And what about other locations such as Poketopia for the battling elite? We could use mini-games and things from the long lost Stadium games, too. Or Pokepark for events or Pokemon interaction (maybe linking it to the island Ash, Misty and Brock left their Pokemon at in Pikachu's Vacation)? Or places like the Ranger Union. If worked on gradually and utilised properly, these regions could add a lot. :3