>>56139834a region with half land and half water could've been cool as shit. give the player surf around halfway through the game, dive shortly after, and have underwater routes with as much location and pokemon diversity as the land routes.
you know the two hoenn fossils? make them not fossils and put them below the water. have a coral reef with wild corsola instead of it being just a fishing encounter. ice floes with spheal basking on them.
if we're talking later gen pokemon as well, there are even more possibilities. mareanie in the aforementioned coral reef. underwater "forests" with skrelp lurking amongst the foilage. non-water aquatic mons like eelektrik, dhelmise, or grapploct. i would love to play a game like this.