Let's pretend that, for whatever reason, Nintendo announces that Gen 7 will be the final generation of pokemon, after which there will be no more mainline games.

What features would you want them to include from earlier games (that were either gen specific or removed after a time for whatever reason) to ensure that it was the best pokemon game ever and a fitting finale for the franchise?

Hard Mode: one region only, or an extremely small new region and ONE old region.