That's not a counter-position, but a challenged original position that doesn't touch the question of how this influences the level of human trafficking. And it's not evidence-based but a naive principle, which again ignores how easily all the supposed protections can be (and over and over again in all the sickening stories, are) sidestepped by the same tools of control.

work permits

This was the part I misunderstood. On this, I'm not entirely negative: a general work permit in place of a job-specific work permit would not tie employment to fully legalised prostitution and would lift the threat of expulsion once the human-trafficked girl is freed (and that's the main reason for the connection to immigration restrictions, I fully agree on that). On the other hand, the main problem I see is still the issue of making nominal legal protections real, as they won't be worth anything as long as the human-trafficked girl interacts with authorities while she has no true control over her papers and money.

_{*Lunatic*, n.
One whose delusions are out of fashion.}