That really is interesting. How are you changing the neighborhood? What are you doing exactly? I'm doing a similar thing but only by flipping houses, which, by the way, is a LOT of work but even more fun than work. Wish more folks would join that contest.
I'm not changing any community buildings yet. I've changed the families as I like. For example, I deleted some boring (to me anyway) families like the Kennedy woman and the Clavells (to be deleted today), and I killed off some sims with the evil trait (I could have played them ages to earn 20K points for the traits change reward but I couldn't be bothered). I've played matchmaker with lots of the single young adults, so there's a lot of new families. And I've given a lot of sims make overs. Like Zelda Mae (now Zelda Frio) looks totally different with her natural hair colour and a cute bandana. And I think Agnes looks way better with the long curly hairstyle from fast lane.
I’ve almost tried this with Sunset Valley once, but ignored a few of the households. It was fun and I had no problems with it for about one generation but then weird stuff started happening like a couple of children disappearing and sim aging acting a little strange. Maybe it's just my computer or something the latest two patches fixed but I'd still advise you to keep the number of children down a bit or the game might suddenly consider the town overpopulated. I'm interested in seeing how this works out for you, good luck.
I hope my children don't start disappearing. Though I have hope that it won't be overpopulated, considering I deleted so many it's adding new ones.
I'm going to have to stop leaving families with a pregnant sim - so annoying to come back to find the baby already born and named. Jefferson? I wouldn't name a kid Jefferson. Though I have Ingrid in mind for Agnes' baby, she named her Patricia, which I don't mind.
EDIT: I just checked back with the Crumplebottoms, and Agnes has somehow joined the stylist career and reached level 8 all on her own! Plus had a baby and all in no time at all! How annoying.