Would love any new careers, and all these ideas are great, but top priorities for me would be:
being able to keep "part time" jobs and NPC jobs as playable throughout a sims lifetime. So, like, Repair Person, Nanny, Maid, ect. Also Masseuse could be on this list. These would be very simple, really only requiring a decent mood, wouldn't have as many stages, and you could have one part time job along with a regular career.
Careers for skills already in game, so: Singer, Dancer, DJ and Yoga Instructor (as a playable careers, or a part time ones as mentioned above), Photographer, Herbalist, ect. I'd also like a playable Veterinary career that doesn't require owning your own pet hospital. What if my sim's just starting out, and needs to gain experience and money before buying their own business?
Basically, before expanding the game any more, I'd like them to look at what they already have and actually make that work.