It actually extends to the whole market, too - if all salaries are transparent, then an RN makes x. They can't make more than that, anywhere they go. It gives a floor, sure - if they get hired, they'll get paid the same as everyone else; it just also makes a ceiling, and, I believe, may slow income growth in general.
So I'd see your point as already happening, companies have already capped salaries, except for executives, who basically set their own salaries.
I love seeing this statement. It's true but the people who post it never follow up evaluating whether or not productivity growth has far out-paced the rise in living standards. If productivity growth has been exponential while the rise in living standards has been linear that's a sign that there's a problem regardless of whether or not living standards have risen.