Ok. Limited amount of families makes sense. In TS2, I created a custom city, put down 6 cheap houses, created 6 families and off we went. I don't know how many families I had for sure when I lost my hard drive years ago. 19 maybe? I like "normal" lifespan so I think that usually takes them to their mid to late 90s. So for me, 5 days rotation was enough to stay in touch with everyone and get them aged together. So when I got to the top of my rotation again, for any kids that were college age, I sent them to school together to rush through it, doing one semester per 5 Sim days. This let the parents age up while the kids were in school and they were usually seniors by the time the kids graduated and became adults.
Having said all that, it might be fun and different to have those 6 founding families but let other families live in the town. This will give match making choices.
I'm pretty techy so reading your description of SP Rotation makes sense in terms of basically stopping any progression on any family I'm not playing. I understand that they are still around which is kind of how it is in TS2. I've had family events and invited family that I wasn't working with so it was kinda cool to see them show up while I wasn't playing them.
I assume once I install this mod, I can use it on a particular town I create, and choose not to use it on other towns like my existing legacy challenge town.
One more clarification: if I understand correctly, if a Sim is pregnant, you can't stop that progression. Correct? This was how I first learned about TS3 when my Sims were having babies without my control, being auto-named, etc.