The trouble with finding any worthwhile model for a country is that prostitution is actually a huge cross border, cross continent big money business. Unless huge changes in the world economic system and societal and gender norms occur there is no system that will protect the underclass most vulnerable. All that will happen is that the underclass changes in nature. Maybe it changes from being indigenous sex workers to immigrant workers or illegal immigrant workers, or just poorer workers. After all prostitution is a business and somebody will always be supplying something cheaper, or maybe more exciting. Sorry to sound pesimistic on this.