I have done that, though I may not be the one your thinking of. The first Uber-hood I did (Uberlicious) was using versions of the pre-mades that I had given plastic surgery too. In that hood, all relationships & friendships were intact (I made sure of that) but no one had any ancestors. I couldn't see the point of making safe copies of the original Ancestors when they were all going to be dead, clogging up the game with their useless character files.
The one I did recently (Megaheaven) was a massive breeding project. Last year, I had created new versions of the pre-made Ancestors (used their genetic info and stuff) and packaged them all up for future use (cleaned up so they are safe). I bred them all (used mods to speed things up), till I got them where I wanted them. In the end, everyone had lots of friends & family, unlike the originals where hardly any of them even knew each other. I divided them up between the base hood and 3 downtowns. Since I didn't kill anyone off, the oldest only have a few days left and the youngest are younger then they are in the original hoods.
Last year I did a different version of the same but I had changed it up by having all the 'required kids' born by the 'correct mothers' but the fathers were chosen by who knocked up the mother first (I use ACR). It was fun to do and I still laugh that Mortimer ended up being Dustin's father.
I like doing breeding projects like this and the pre-mades give me a plan to follow, though I've done some hoods with my own sims. TS2 hoods & TS3 worlds are fun to make and share. :smile: