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

An actual good survival zombie MMO. Ala what day z and h1z1 were supposed to be. H1z1 had the idea to be a procedurally generated middle america setting that sounded amazing. But it turned into a battle royal. Day Z was supposed to be the hardcore survival zombie but it's too just turned into essentially a battle royal. I don't know. I know there has been so many in that genre but I don't feel like any of the ones I've played hit it right. 7 days to die is maybe the closest and I also really liked project zomboid too. I guess I thought dayz captured the realism of the combat with it's arma roots.