I will add my vote to the growing list of people that would like to see Midnight carry on the family legacy. How awesome would that be, a sixteen-generation immortal dynasty? Kind of, I mean, I know it's not like that exactly, but that's pretty close.
Also, I vote for Appaloosa Plains because you asked for a town that would be less likely to run out of townies, and that town has the most already-pregnant Sims I have ever seen. That has to have some influence on it, right? I see it as a growing town because of this. Also, speaking from experience, while I love Twinbrook it is somewhat difficult cramming all those people and lives into 40x40, if you don't have a strong reason to use Twinbrook I would say go for the nice big 64x64 lot AP can offer.