A legal brothel would protect girls against mental and physical abuse from pimps, and customers from deseise. The problem would be the after market. Young girls below 18. A legal brothel would not want to house them, so they would be left out. Of course it goes without saying that we would rather there not be girls younger than 18 in that profession, but wishing and doing are two different things.
We would have to have REAL police intervention for under age girls, and prosecutions for the males to deter it.. The numbers might be too great for serious police and court intervention. That's why I thihk concentrating on child pornogrophy and prostitution amonst very young girls must take priority, and leave the rest to brothels.
With the advent of the internet for solicitation, a new form of police detective is needed as well.