Hiring fighters who have surrendered, in a war of this type, is an old, and usually successful, practice. You cannot do it, however, until the population you are recruiting from has decided to work with you, and not against you.
India has been fighting Islamic radical separatists in Kashmir (northwest India) for over fifteen years. Most of the separatist groups have agreed to negotiate a peace deal, and India has decided the time is right to recruit a paramilitary force from among the separatist fighters who have disarmed recently. The remaining Islamic fighters have been spending a lot of time trying to terrorize the other residents of Kashmir to either side with them (if they are Moslem) or get out of the area (if they are not.) The fighting has ruined the once prosperous tourist economy, but that is coming back now as more areas are pacified. The new paramilitary troops would be assigned to keep the remaining Islamic terrorists away from the population. This would be various forms of guard duty, aided by the experience many of these troops had in irregular warfare when they were on the other side.