Pets, well, at least dogs - with dog grooming, breeding and training professions please. I'd love to be able to dress up a sim pet, train and show them as well.
Cars, motorcycles, bikes, garages, skateboards, rollerskates, rickshaws, (modes of travel).
Community College and University where we get to follow the sim to class in a similar mode as the "Get to Work" professions. Perhaps what the sims do in class can affect their grades somehow?
More follow-your-sim-to-work careers in general. How about car mechanic (to work with the vehicles)? Daycare worker (to go with Parenthood)?
A tool for making more walls and floors (like Homecrafter).
Building and furniture packs that are style specific like Art Nouveau, Arts and Crafts or 60s Vintage.
A way to replace the existing color choices with our own. I would not mind copying over the current choices or having even one or two "variable" slots. It would be nice to be able to coordinate decor and outfits better. Nothing matches in the current choices.
Change the frog textures to something that matches the description of the frog. This may seem like a little thing, but since the textures are there anyway, why not have real blue frogs and pretty frog colors?
Beaches, water, diving, mermaids, boating (collectible pearls and shells).
A way to merge rooms in the build mode so that we don't have to plan out our drawing strategy at the beginning.