Regional variants from all generations with some real thought put into them
Riding Pokemon to be expanded to any Pokemon big enough, and any of those that should be able to surf can be used in water
Gyms back (or whatever replaces trials to be more like gyms than trials)
Bigger areas than Alola
Diving to return like RSE but expanded with more interesting locations (like a coral reef instead of just a seafloor)
And for some more specific and unreasonable hopes
You and rival join opposite teams at the beginning. Neither team starts evil but both are competing for resources, and as you, the protagonist, manage to take the resources/pokemon the other team is also going for, they start to turn to questionable methods. At the climax of the story, you convince your rival that what their team is doing is wrong and together you stop their team's evil/dangerous plan. Kinda like RSE except you're more involved and it's more personal and the goals would be less stupid
Alternative thing I think would be cool is if the region were (roughly) a circle and one version starts you on the west side of the region and you go clockwise through the gyms and the league is in the center, and same for the other version but it starts you on the east side of the region. So gyms 1-4 in version A would be gyms 5-8 in version B, and gyms 5-8 in version A would be gyms 1-4 in version B. Obviously the gyms and Pokemon would scale as well, so early-mid game Pokemon in version A would be mid-late game Pokemon in version B, and vice versa. The stories would be related, but not identical, and on TVs you could read reports of what was happening in the other version.
