New and Different expansion type: Wasteland? Hear me out.
What if instead of having a world that is already set up with buildings and characters, you have a complete clean slate.
Many simmers, other than me, LOVE having the control and option to add more than just regular items; one example is using the debug option where you can use many live objects. What if there was a type of wasteland or clean slate where you can completely edit the world.
It's already been proven that when you give the creative option to simmers, it's used until all options are exhausted. What if there was a expansion that was dedicated to those simmers who would love to make their own type of worlds?
If we want a huge lake in the middle of the map, we can make it. If we want tall or low mountains with a waterfall, we can make it. The options and how far this idea can branch is endless and could also give something different in The Sims 4. It's not like we can't already do it, but we're restricted within the plot lines. Maybe they could create bigger plot lines that could hold such imaginations?
I have two suggestions...
There are completely blank, all-lots-bulldozed save files available on the Internet that might suit your needs.
There's a new Create-A-World mod by Twisted Mexi that's in Alpha right now (which means it's a very early "testing" release). I would only use this if you want to help him test the mod, since it's so early in the process, and also it's a patreon download, but... it's coming eventually.