You do not "need a mod" to import sims. All I do is import the first one to a lot. You can then evict them. You can then easily add sims from CAS to the world by just doing the same, but can bypass putting them on a lot by exiting out of the place on lot screen. I don't use a mod to import sims. It can take me maybe 10 to 15 minutes to import a dozen different households. Btw, I play via PC.
I do this but in all honesty, having a saved no time played (as every EP I pretty much have to re-do this to prevent bugs) world template file, and edit/manage world before creating/playing households first (like in Sims 3) would be just so helpful.
