I know this would be an expansion pack rather than base game, but I would love for apartments to be customizable (Sims 2-style).
I think basic small pets should be included in base game, though. I did not like the way TS4 delivered small pets and would love to know who thought omitting them from the Pets expansion pack and packaging them in a separate pack was a good idea.
I also think after-school activities (I don't mind if they're rabbit holes) would be nice. After-work activities could be a nice way to meet and befriend coworkers. It could pop up as an opportunity to go grab food as a group or an office party.