Back to the topic at hand.
Minimum wage can provide a hedge against slave labor, yes. But left to it's own accord without restrictions, it can cause havoc on a nation.
One possible way to compensate for this threat is to set a maximum minimum wage, however, if the maximum is permanently set, then this too can cause problems. if it's set too high, it is almost as bad as if it where a free range minimum wage. If it's too low, it can cause people to migrate to other nations that have a higher minimum wage and similar freedoms and such.
Alternately, you could set an adjustable equation system for minimum wage. while such a system is adjustable, well-defined, and less likely to be corruptible, creating such a system is complicated to create, and would be quite hard to nearly imposable for an existing nation to switch to. In order to test this, one would either need to build a simulation or find a new or relatively young nation to test this system