Agreed, that would be handy. It's frustrating that if you make a sim then want to add their parents or adult children, you can't give them skills and careers when they would realistically have them. It's the same with teens and children, some skills would be handy.
As a side note, I noticed recently that I couldn't even have 2 "story" generated sims in the same household but I used to be able to, so I don't know if it's a mod conflict or an update.
Personally I would really love to be able to set skills and careers without having to go through the quiz, and would love to be able to do those things for sims of all ages (according to their age). For example, perhaps each age range should have a range of benefits that can be applied in CAS.