One feature I would really like to see in the game is the ability to hire NPCs into your faction. If I'm not mistaken, there's a cap on how many people you can hire into your squad (I can't remember the number off the top of my head) and this would make it harder to have multiple fortified locations with guards and labourers.
Well, anyways that's it, there's my suggestion and all I have left to say is the game is great and keep up the good work!