I would love a Monster Hunter game where you basically have all the zones mashed up into one big one. So instead of having a forest zone with 11 areas, a swamp zone with 11 areas, a desert zone with 11 areas, a tundra zone with 11 areas, and a volcano zone with 11 areas, you'd have one giant zone with 55 areas that encompasses forest, desert, swamp, tundra, and volcano themes. They could maybe gate off sections of the world until you reach higher hunter ranks, so you can't just access everything immediately.
The main thing this would fix is the repetition of areas within a zone. There's a significant problem where many monsters follow the exact same patrol patterns in each zone. In MH4U's Volcanic Hollow, Brachydios, Stygian Zinogre, Gravios, Teostra, etc. all go through the same areas as each other, since there are a limited number of areas for combat in Volcanic Hollow. So fights with different monsters all feel very similar. By connecting all the zones, you can have many more areas available. Like Stygian Zinogre might move between the volcano and tundra zone areas, Gravios might move between the volcano and swamp zone areas, Teostra might move between the volcano and desert zone areas, etc.
Plus, it would expand the number of available areas for each monster, which means less shit like constantly fighting giant monsters in the tiny area 2 of Volcanic Hollow.
The main issue with this idea I see is that it would make for a ludicrously complex map, which would be pretty confusing if not handled correctly.
(In case it's not obvious from the rest of this post, I fucking hate Volcanic Hollow)