Yes! I would love to get a kit or stuff pack that's basically a new Newcrest; an empty world with empty lots of varying sizes to build on. A pack/kit for builders. It doesn't even need to feature new build items, if you own just a few packs you already have many more build items than you can reasonably use.
It's so easy as an avid builder to run out of free lots to use, and then you have to start bulldozing lots you might actually want to keep. I personally love to build many different community lots and visit them with my played households. I love building and revisiting many different types of lots. And if you play like that, you end up considering to buy new packs just because you need new real state to keep building. The focus of EPs and GPs is gameplay, and they all add things to your game, but sometimes those are things you don't want. I don't care for supernatural stuff for example, I don't want vampires or werewolves or more ghosts, that doesn't fit my gameplay style, so I don't buy the packs that focus on that stuff, because I would just find these packs' features annoying. I'm not buying packs that have various features that I am not interested in or would find actively disruptive to how I want to play. And with the diversity of themes covered by the various expansions, I might not be the only player who doesn't want all GPs/Eps because some cater to gameplay they don't like.
Offering world kits/packs caters to everyone who loves to build, and allows people to expand their worlds without having to add gameplay they don't care for just to get more space in their worlds.
Worlds with new themes would be fun, yes please Africa and Australia themed worlds!
But I would also appreciate world kits where the theme of the empty world matches existing worlds. Let me build another neighbourhood in Willow Creek. A lot of our existing worlds seem to be big cities, give us a few more neighbourhoods as add-ons. Add-on worlds would be less work to make and could probably be kits, completely new worlds with new debug items and some lore and maybe some local architectural elements to use could maybe be stuff packs. We get the courtyard oasis kit with Moroccan themed items, it would be fun to have a matching world to it so we can build a small Moroccan town, for example. A Serengeti or an Australia pack would need more specific assets to do it justice than another neighbourhood or two for Willow Creek or San Myshuno.