>>35111534More Pokémon species that their own unique behaviours and gimmicks.
Enemy Pokémon that use items.
Level reset dungeons that have unique dungeon layouts, graphics and gimmicks
Said dungeons would also have a story, or a continuation of the main story, that does not get in the way but can still be enjoyable (think something like Joyous Tower or Buried Relic but more fleshed out)
Missions like in the previous games, but also a side quest system that works like the missions from Super, while having something to distinguish them from the regular ones, like including a side story focusing on the secondary characters or include some non-randomized challenges.
A combination of Emeras and IQ, while also making sure the latter isn't just grinding, making it more useful and enjoyable.
Mysteriousity from Gates to Infinity.