Other than for additional open water (which would be absolutely awesome and I am all for it everywhere especially islands)
I don't really think they'd need to expand every single world with shopping areas or campus areas or such
what i'd have interest in is giving more lots in neighborhoods that have frustrating amount of shells
such as del sol starter area or sulani village (definition being there is way more shells than actual lots)
or even just toggles to simply turn on/off viewing the house shells in neighborhoods like newcrest ones
so they just kinda disappear and you just see some mmm green lawn/trees and stuff there like good old ts2
like there is plenty good lots there but i absolutely hate the house shells in that world so i never use it
