This is an excellent suggestion. Maybe there could be an added quest type: capturing enemies and rivals alive (you only get paid or you only get paid the full amount if they are captured alive). Maybe you could also capture nobles and ransom them (for a rep hit with that family).
Your hostage could take a slot on your roster. They might try to escape and others might try to rescue them.
Oh, maybe there could be an additional quest type: transport prisoner(s). Like a delivery quest, but you have to transport a person (often against their will). You could also ‘escort’ a daughter to an arranged marriage–but where her lover might try to intervene). Etc.
