I've never played TS3, but watching some video on Youtube I've noticed that something similar was already made in TS3! I'm not sure if it only worked with Plantsims, but taking a DNA sample from them and using special machine would result in having a baby-clone of that sim!
In TS4 it would be greate to have something similar. The difference between using clonning machine on an adult sim and on a DNA sample would be that adult sim results in the adult clone, and using a DNA sample would result in baby-clone.
Wouldn't that be awesome??