It seems like there are two conflicting forces here. We want to ensure that we accept mostly high-skilled immigrants, so we can't do a pure lottery. But anything less than a pure lottery and immigrants are forced to "perform" or be kicked from the country, they will end up "both paid lower and unable to escape abuse" as you say. I don't know that it's possible to solve this satisfactorily.
Why is a lottery necessary? There is a quota so why not fill it with those being paid the highest compensation? What's wrong with a market solution? It would bring in those who are most in demand. What better way to measure demand than prices?
