Make A Backrooms game

I am trying to make a co-op backrooms game for Xbox. Its going to be a big game, hoping to make it to either a multiplayer co-op game or a mmo. I want the game done in either unreal or unity mainly unreal. There's no deadline, although I would hope to make it come out by this year.
These are the top 3 games that I like to reference off for my game:
https://store.steampowered.com/app/1963190/The_Backrooms_World/
https://store.steampowered.com/app/1987080/Inside_the_Backrooms/
https://store.steampowered.com/app/1943950/Escape_the_Backrooms/