Its a simple idea spurred on by the recent developments of a sort of neat exploit developed by @Rumrusher where adventurers can call back citizens with promises of artifacts supplied in fortress mode, retire the adventurer then have the people who have been lead back to the fort embark onto a raid and return to become full fledged interactable members.
The recruitment missions works by means of sending out conversational militia dwarves, who will then work for a month or series of weeks asking around the settlement in a similar fashion to artifact questers or villians digging for intrigue agents. When they have completed their task they will return to the fortress and report back how many people they have recruited sorted by name, race and profession.
Instead of following the dwarf back, the people will remain on the controlled site, people recruited from foriegn economically linked settlements (because the link may make them more liable to join) will join the visitor pool to likely ask for long term residences; & recruitment upon hostile but not at war sites like Goblins are accessed by stealth (ambusher) skill to find defectors and symptathists.
Some additional details to add onto this suggestion are
- Lords and ladies in your fortress by inheritance have a stronger effect upon recruiting, as recruiting from provinces they belong to and 'rule over' will flip the population to your government, all willing people will join and those who are not convinced or compelled by duty may be kicked out, exiled (or mutilated depending on ethics).
- Monarch level positions can oblige the local rulers to commit, but if they are rejected (poor speaking or winning point of counter arguement against the diplomat) they can rebel and become independent with a big hostility spike.
- Refusal can lead to a negative social impact individually or if its escalated by people reporting your dwarf to the guards/site ruler in the worst case scenario, your recruiting dwarf can end up being arrested, or starting a hostile, possibly doomed engagement against the site.
If your site has a poor reputation with a Civ by repeated diplomatic faux pas or a common tendency for dwarves to die horribly, it will raise the ceiling of the
manipulation and white lies skill relied upon persuasive arguement to bring people to you. Of course also needing to be both rich in status, value, offerings and have liked or least popular leaders as buffs to have people flock to you instead of run away screaming from your death-fort.