This is basically the methadone approach, but when I was in general practice, just try weaning people off anything they have a dependence on that they're not motivated to stop using.
Plus, harm reduction like syringe services (i.e., needle exchange) is already hugely controversial for "encouraging drug use." That sentiment is at best arguable and at worst a reductionist distortion, but it becomes even harder to argue against when you're in the business of handing out better dope.
