Oh my goodness, a marriage therapist would be hilarious. Follow them to work like in GTW and deal with different dynamics among different couples. That would be so great.
An active teacher career would be a lot of fun too. Grading papers, scolding students, picking favourites. SO many opportunities.
Also, part time jobs for adults. I know you can mod it, but it'd be a nice touch. Not everyone wants to work five days a week!
Finally, a butler/maid job would be REALLY cool. You go to the sims house for the day and repair things, clean, cook - everything NPCs do when you hire them. A gardener could be interesting too.