What is a video game that you'd love to play, but no one has developed yet?

A mix between world strategy like europa/total war, management of dynasty/kingdom/territory like crusader king, that can lead into invasion with advantages due to planning/bonuses in an RTS like like rise of nation bonus, extra armies etc , and rts like age of empire/mythology rise of natio , etc. That you can then further go into a single player hack&slash like mount & blade, or an fps like CoD or battlefield, where you are a singular soldier/leader.

And with a significant time progression, such as going from stone age with clubs, to medieval, to modern with guns, to futuristic with space age and all.

And it'd be very cool if you can basically hotswap between those. As in, you can go into the overworld, manage your empire, go back to rts to make units in a settlement getting attacked to defend it, and then realize you are losing on a front somewhere so you go full try hard with solo fps to try to hero your way to victory yourself.

Will real time progression between all the environments ( not at the same scale of speed tho ), so you would be hard pressed to play on every front at once yourself, you gotta make choice on which part you do yourself to 'guarantee' a win, and what you hope the ai will do enough to win by itself, or maybe pop over there shorty to give yourself a boost or massacre a bunch of enemies in fps mode to make sure your ai can make work of the rest itself.

Don't think this will ever see the light of day. Waaaaaaay too big. It's litterally multiple levels of very different games/genras mashed together, at once, and in parallel