i would argue the way sex workers get customers is at the core of your complaints about sexwork. you'll still need pimps if the johns need to vet/be vetted to avoid getting arrested, it's part of the reason they exist now. the other component, safety, is not affected so much by the legal immunity you propose, because everyone involved except the sexworker are committing illegal acts, and so the trade is still secret & incentives to not report/act on abuse remain for those parties---even for the SWs who might still risk their livelihood.

if neither party is committing a crime, the reasons for a broker diminish, or their role more resembles an agent. if a crime is committed any party can call for help, not just the sexworker. for the record i'm advocating decriminalization, not legalization into designated brothels in designated districts