I constantly edit my townies. It's just something I started to do a long time ago. I think I started doing it because there were too many poorly dressed, idiotic costumed, and to be perfectly honest, downright ugly Sims. I know, beauty is in the eye of the beholder and all that but I'm the beholder whose eye is doing the observing.
Frankly, I'm finding way too many senior citizens in my town walking around they are on their last legs. Just because I'm a senior citizen myself doesn't mean I want to hang out with them on the Sims where they are pretty clunky and about as spry as a block of wood. And if I like the result I save them in my library with the intention of populating a whole town with my recreations eventually.
So now, using mods of course, I'll edit them, change their age etc. etc etc. Can't age them down to teens though because the game won't let me come out of CAS if I do. If there's a mod for that already like there was in Sims 3, or if someone makes one, that would be nice.