I've always wanted a prison to control, and since a Stronghold is in the making I would just like to throw this idea out there.
Picture having your own, scary prison and decide for yourself who is going to end up in that prison. Maybe there are people in this world that strongly disagree with your religious views? Maybe your just an evil soul that finds pleasure in having power? Or maybe you're a good person with good intentions - throwing thiefs, murderers and pillagers behind bars, never to see sunlight again?
Maybe in addition there could be mercenaries/guards that you can hire for your Stronghold to haunt the people you want behind bars down. They could have a chance of not being able to take the prisoner as he/she have people watching their backs - which would mean you need to hire new guards (money sink right there).
Or maybe force prisoners with other religions to convert to your own faith? Granting the player's character either the illusion or the fact of getting closer to a "god".
Prisoners could also have the ability to escape. Or maybe some of your own guards aren't that loyal to you as a leader? There could be sort of a moral system involved with your people - with low moral they could have a bigger chance of taking money from pisoners and help them escape instead of keeping them inside.
Of course I wouldn't want these guards to have an impact on the players journey outside the Stronghold.
Some of these guards might be mercenaries that you could hire for your own expeditions - but I wouldn't want them to have the same impact as followers have.
It's just an idea. I think it would fit with the "mature" theme. I wouldn't be suprised if you guys/gals think this wouldn't fit a cRPG, but I'd still like to see this in a game.