I propose that, rather than a system of recruiting someone into your ranks of trustworthy colonists, if the prisoner's chance is really low, then once you 'recruit' them they will attempt to walk off or go on rampages repeatedly, until you increase there trust and faith in the colony enough that they feel it's there best choice to join the colony. (And then there would be some you just can't recruit without them walking off/ attacking you)
This would create an interesting dynamic of "Do i trust this psychopathic cannibalistic tribesman as a colonist?"
This would create an interesting dynamic of "Do i trust this psychopathic cannibalistic tribesman as a colonist?"