I think (without knowing the code) Cults do build more mansions the longer you let them live. And those mansions will improve over time, fielded or let's say fieldable personnel -wise. If you can handle them, they're good for score, training, bounty, but: you need to discover them, first, and existing mansions seem to behave like alien bases in the original game, giving you a negative score while they exist (best observable at the beginning of every month, when you start out in the negative; means some bad things are going on).