Regular townies turning into spellcasters?

I think they made it this way to keep from generating too many sims... eventually it's going to just be too many with new packs still coming in. Like if we get a Uni pack I doubt they will pull normal sims into Professor jobs and we will need generated students ect. Our game generates a lot of sims and it weighs in the background.
I can see it becoming a problem when I move to another save but if I know what to do about it before hand prep wise I'm good with it personally. I plan on playing the sims I want to keep safe and using that suggestion to make a spellcaster household - unplayed. So the game can pull them in.