>>52208814I could see it working in a more limited setting, like a solar system that works like the islands of Alola, as separate planets that you travel between. Each has a unique environment that's in some way hostile to non-native species. Like a Mars-style planet with continuous special Sandstorm or Sunny Day type natural effects that local Pokemon are immune to, but others are not unless they're of certain typings. Of course, they could and should be more imaginative than just "Mars, but in Pokémon" and create vivid and lively planets, which still feel very alien, but ultimately fitting into Pokémon.
Story-wise I could see it being set in near future, the protagonist(s) being young adults who have just transferred on the Moon to a research station led by a Professor character, who leads a group of scientists who study the Pokémon living on other planets of the solar system, which became as a surprise to humanity as they started expanding elsewhere.
The problem with this is that aside from very few, specific Pokémon like Clefairy, you couldn't really have most Pokémon appear in space. If half of the game was still set on the main planet, that'd be an entirely different story however. The could be a large hub-area on Earth with a large city, the "cities" on other planets mostly being research settlements etc.
I do like the idea of some rogue band having turned Space Pirates being the bad guys. I wouldn't necessarily want to see actual intelligent alien species though, but at most signs of an ancient one, relating to the obligatory end-game legendaries and through them, to the story itself.
