Is there any possibility of making a tool that lets you add more lots to existing worlds?

I feel like almost all of them are so pared down and there’s so much unutilized space that could have had functional lots on them. There’s so many dummy houses to make the towns look bigger and I wish we could have to ability to make actual houses in some of those spaces

Idk if it’s possible, I know someone is working on a mod to be able to make fully custom worlds but I would be happy with just being able to add more lots to existing worlds. I would imagine it would be a tool people can use to make their own customized version of the world and then others could download it too