The problems you identify are indeed significant. I guess that I might be a closet member of the flat earth society because I just don't get into globalism. A system of managing global pay equity implies a system of global pay equity management. With all due respect to the Americans and Europeans in this audience I suggest that the management of the global pay equity process would be subsumed within a white positivist north american-centric paradigm. While that would ultimately be good for American business the rest of us would suffer.
Labour laws are foundational to national governance.
As a country gives away such law making capability, it's economy will be subjugated to external economic interests, to the dis-benefit of it's citizens. All of that is not to say that the problem of worker exploitation is to hard and should therefore be ignored. But the solution must come from the industrialised countries in a non paternalistic and therefore non global process fashion. And there is the rub. I doubt it.