The Romans increasingly relied on that strategy with the Germans. Shortly thereafter (in historical terms) Roman greatness was gone, and replaced by the 'barbarians' that formed the heart of their military.
Military service, separating the wheat from the chaff. I can’t think of a bettor organization suited for this purpose.
Good point. A lot would depend on why the illegal immigrant left his country of origin. Those who just want a job, no thanks. Even those who are seeking asylum may not appreciate what it means to be an American and may not be a loyal citizen. Those who want freedom, who are willing to take America’s heritage as their own (doesn’t mean they have to forget their family heritage) and who are willing to give their all to an adopted country, would be most welcome.