The main things I want the most, and have since Sims 4 came out 9 years ago, is the ability to build apartments like we could in Sims 2. I was so disappointed, as many were, when City Living came out and did not have this option. I am hoping this new EP leak is true and finally allows apt building. Next, I would really like to be able to favourite cas, build and buy mode items so I do not have to spend so much time searching for things I use often. Also, without having to use a mod that does not work very well, be able to have more than 8 sims in one family and not count pets as one of those allowed, example allow 20 sims per family and 10 pets, or even 12 sims and 8 pets. 8 is just too low of a number especially when having a pet uses one of those spots.
Other-
Pool/swimming activities - swim up bar, pool slide, pool volleyball/basketball, other games.
Live in Nanny
Butler fixes so they actually do their job- ability to click on item and have option "tell butler to clean up"
Building options-
Be able to build split levels
Bring basements above ground and be able to put windows in the basement without having gaps in the terrain around the house
Round/curved pools
Build a hot tub right into a pool
Sliders for curtain so they fit properly
Platforms and Foundations fix - where you can easily make different sizes attached to each other, where raising or lowering one doesn't do it for all. (For example build a garage that is ground level attached to the house that is a few notches
Slider tools for some of the wall paints to adjust the colour.
Auto Roof tool, and more roof building options that make it easier to smooth one roof piece into another.
Stairs fix so when you have split stairs it does not show a line on the outside of the house.
In CAS I would like sliders to give sims different heights.
Ability to copy and paste sim so you can create identical sims for creating twins and change the sex where it will keep the basics (skin, hair, facial features).
Also, super important, the ability to turn certain pack aspects off completely. For example use the world and items in Get Famous, but have fame/celebrities completely turned off, or use Vampires items, but turn off vampires and so on.