I'd reeeeeeallly like to be able to recreate Moonlight Bay from Sims 360, but I don't want to mess with unstable world clone mods. Maybe Maxis will drop a create-a-world near the end of Sims 4?
I dont know if a tool for creating a world from scratch would be ever possible, but i can see them providing tools to allow us to customize the current ones as much as possible