Suppose all non-US-citizens working in the US had to be paid at least at the 60th percentile of what US citizens earn in their job description. They can come to the US and be an engineer or construction worker, but they can't undercut wages. And the penalty for underpaying immigrants is simply that they get their back wages plus interest.

Immigration enforcement would concentrate on employers, not migrants, and they wouldn't risk deportation if they reported exploitation.