Well, of course, I want Seasons back. Everyone says that. :-) I miss my Plantsims something fierce, though.
I'd forever and always like to have more recipes for them to cook. Of course, I guess that'd make the "pie" menu unmanageable. Maybe some more snack options, not just juice and bread with jam. What if my sims want nachos? (Of course, I guess I should just get WA so I can have more food, huh?)
What about boats? I know, good luck with performance on something like that, but still. Building houseboats instead of just houses. There's all this water around town that they can't interact with.