We can just import foreigners and train them to these jobs — right?
It appears that some, are self-importing, almost automatically and continuously.
Yes, this is the strategy. Same as Europe had when it decided to let in waves of immigrants from the middle east. The idea was to have a permanent underclass to do the dirty work while the natives would be free to write poetry or study literature or whatever. They never said that out loud but that was the idea. Unfortunately for them, the 2nd generation of immigrants have fallen into three bins: hard workers (yup, there are some), welfare takers (burden on society), and angry powder kegs. Oops, didn't plan those last two!