I don't think it'd be possible to without mods, like you said. I mean, there's not only the townies but there's downtownies and the vacation townies. There's special townies like the vampires, the fire dancers, the social workers, maids, service sims in general, garden club member, etc. I don't think those can be created without a mod and therefore it doesn't seem possible that you'd be able to create a neighborhood without townies. There's also the dormies, and all of the pets that get auto added to new neighborhoods.
I am not saying it's for certain impossible as I have never tried...but it does just seem like there's too much reliance on all the townies to not have them auto generated.
