>>56136402I still think a region based on either the West Coast of the US, New Zealand, or the Mediterranean coast (Riviera down Italian coast) would be the greatest choices and can be done beautifully!
Thematically, I think Gamefreak should return to shallow existentialism and highlight themes of nature and technology.
Nature is what keeps the world balanced and healthy, providing natural beauty and abundance of exotic landscapes. Nature, however, also lacks an ability to propel itself forward to the future, capping human progress.
Technology brings utility, convenience, advancement in many areas of society and for human growth. However, technology also poisons and pollutes.
Each has a downside that could be explored in the games setup and worldbuilding by having the villain team by in the "morally grey" area and attempting to hyper-technologize society and have the legendary Pokemon be parts of nature again to restore balance.
Dawn and Dusk would be good titles, but feel too close to Sun and Moon at this point, though.
Region could introduce a new "gym" mechanic and say goodbye to the boring school mechanics they've been using lately. An Elite 4 team comprised of actual strong trainers or even a tournament-style competition to become champion could be used. You could amp it up by having the tournament be able to be done online, essentially building in wifi battling into the game's architecture and world-building by facing REAL trainers to climb to be champion (obviously you could also do it using NPCs and offline).
Bring back a whole new slate of Pokemon plus common Gen 1-5 mons and Gen 7 mons (if it is set in Australia or West Coast US), or use common Gen 6, 8 and 9 mons (if it's elsewhere in Europe). Finding a more balanced way to highlight some of the Pokemon could be done this way if they actually put in effort with the distribution (i.e. no way I should be seeing something like a Flamigo in a PNW region or a Comfey in Italy).