A singleplayer open-world sandbox RPG in the vein of Skyrim, but you have powerful abilities on cooldowns like in MOBAs/Overwatch, command troops like in Mount & Blade/Blood of Steel/Conqueror's Blade, and can go around conquering cities/developing your own nation culturally/socially/technologically/economically/etc. like Civilization but more open-ended where you can do things like decide actual religious doctrine and encourage specific aesthetics/music/social norms.
Obviously, though, such a game is incredibly ambitious and I don't think it'll ever be made, as it takes the most unique and hardest-to-make parts of several other games and then combines them. Still, I'd love to play it.
That's similar to what i want to make. An open world where every npc and enemy has their own life and you can do anything, even start a settlement and grow it into a kingdom.
It's just so much work, and procedural generation takes a lot to not be bland (hand crafting would take a huge team of artists and designers). I'v scaled back the design two times and magnitudes, and it still seems big. (PS It's just a hobby for me, so don't expect anything)
Dwarf fortress is probably the best at it and it took a talented person a long time to get even to this point, not to mention it's 2d squares.