I would love a Time Travel EP that included all the historical worlds: Caveman/Prehistoric (cave living and bonfire outdoor fireplaces), Ancient Egypt, Ancient Greece (pillars, the Odyssey, the Alexandrian Library), Ancient Rome (aqueducts, bathhouses (cross between hot tub and sauna and pool as a community lot), soldiers, gladiators, and military culture - excess violence could be blurred out or removed by looking away in a cutscene to watch other Sims reactions), Medieval (welcome back Sims Medieval), Renaissance (functional non-wishing wells that only make water available, more artistic murals in different styles, glass blowing, more stained glass windows and doors and more wood carving and statue carving options), ancient Celtic (Stonehenge, spellcaster extension (nature magic, pet magic), rabbits, maybe even igloos or ice sculptures), ancient China (sculpting, pottery, Great Wall, incense shop, cultural fashions), Victorian (England) - corsets, lace, horses and carriages, Wild (American) West (cactuses, Wild West decor, Wild West bar decor and furniture, wool and leather, buffalos, board games, showdown at noon - with fingers!) , plus maybe a futuristic world (although Batuu kind of covers futuristic). All the past worlds would ALL be off the grid except maybe Wild West. We also need more off the grid lighting of all kinds, and more plumbing available off the grid (all sinks should probably be off the grid).
Classic movie sets (from Get Famous) made playable would be perfect here. The Time travel world (if only one world was added) would show a wormhole or spiral symbol, with description, and should all be vacation worlds. However, PLEASE don't permanently break the phones: the phones should have current internet/phone capacity greyed out and social bunny notifications removed except "travel" while time travelling.
Another thing I wouldn't mind seeing is a crossover pack world... kind of like they did with Batuu, only with mobile games like Love Nikki or Shining Nikki (fashion or nail salon design), Gardenscapes (landscaping and garden design), Homescapes (home design), Minecraft, Fate of the Empress (classic Chinese choices game with lots of related fashion), Bermuda Adventures (island crafting game), Fishdom (aquarium game), Sims 4 mobile, and Sims Freeplay. A LOT of mobile games cross-promote other mobile games. Also, maybe pull in the Mining and collectibles crafting from Stardew Valley. (Yes, you can actually make clothes in SV by combining artifacts and cloth.) Speaking of which, I do wish the Sims Cottage Living had included wool-producing animals.
A sports world would also be great: put a stadium on a 64x64 community lot or introduce a larger lot size. Maybe do it like the Olympics: different Olympic events on different lots and/or change up the sports by season. For those without this pack, going to a sports event could be a rabbit-hole, like attending religious services on a holiday event.