Not sure if this is in the right forum, but whatever. :P
Exposition: GSC had not only Johto, but a somewhat scaled-down-in-story Kanto that could be explored after the Elite Four was beaten and showed what happened to it three years after RBY. Here on the Internet I've seen some people who were fine with this and liked the nostalgia trip, while others who didn't like that it was included, rehashed, and say that they should've focused on making Johto better.
But my question is--if you made a new regular Pokémon game, but with two, three, or heck, all regions--how would you make it remain fun and engrossing? (This is assuming it's a good idea in the first place, of course.)
Myself--the only way I can think of right now is not introducing each region linearly and making the player necessarily doing the same thing in each region (e.g. beating each region's Gym Leader one by one). Instead, locations (not necessarily in the order of the regions) could be introduced due to an unorthodox frame story. What kind of story that would be doesn't really matter--as long as it's not just the orthodox get-all-eight-badges story. And--heaven forbid--a complex plot. :P
How would you do it?