It could be interesting to have a first person 4x, where the player is a unit in the game (the leader) and only has local information. Up until the information age it would be mostly played by letters delivered on horseback. Perhaps also state visits and talking to other nations' diplomats.
I've had extensive thoughts about a space-based coöp 4X-like game with fog of war - jump drives can only take you near the speed of light (skipping the need for fueling g-drives and forbidding unstoppable kinetic kills), not faster, so you have to send one or more players to each system if you want to make decisions there without waiting multiple in-game years. The nice thing about relativity is that it doesn't matter if all your players are active at the same time, since the causation won't reach anyone for a while.
I did prove that this general kind of "blind coop" game/quest can be fun in a different setting ... but it was way too much work without more automation than I managed to implement. Balance and mechanics are hard to get right with constraints like this, and AIs are dumb so it's hard to automate your testing ... for something the players (and QM) will probably only stick around for once.
Yeah that would be good, that fixes the complexity in control that spirals once your civ blobs. Keeping it simple and streamlined across the entire playthrough is important.
I think it would be fun to maybe not even be entirely aligned with one country and act as some sort of third party that can impact the growth or decline of other empires. So the AI is still playing the 4x around you but you're not locked into a given team.
This might allow you to pick and choose some of the fun parts (e.g. exploring for a given civ at the start of the game, or picking a expansion spot for their second city) while sidelining the less fun parts.
