Germany originally planned to bring Turkish guest workers for two years at a time on a non-immigration basis. Maintaining that temporary status proved impossible. In the oughts, Germany had to change its naturalization laws to provide a mechanism for permanent residency and citizenship. But decades of living as second-class non-citizens resulted in lack of assimilation: http://www.spiegel.de/international/germany/turkish-immigrat....

(The integration part is a touchy subject in Germany. My point more directed at the idea that you can have a country with a permanent class of non-citizen immigrant workers. You probably cannot do that in a liberal Western democracy.)