So, before we can get funding for treatment we need public will, right?
So long as they are viewed as degenerates unwilling to engage in basic care, there will never be the public will. And for some they wouldn't take the help even if it was available, because for a minority it is in fact a lifestyle choice.
Given both those facts, the first step to getting public will for treatment is to minimize the negative perceptions of the class, which is best achieved in the immediate term by reducing visibility, specifically of the street drug addicts.
Combine with safe supply and direct interventionist supports (room checks, emergency buttons, etc) and there would be both an immediate improvement in QoL, individual outcomes and public sentiment towards further supports.
A key is to not permit use in rooms but only at safe sites within the building. Rule violation would mean switching to a monitored room (camera to ensure no drug abuse).
One issue underlying all of this though so that such systems simply can't work for those who suffered abuse by the system in the past, there's too many of our visible homeless and drug users who are where they are almost exclusively because of abuses in foster care or imprisonment (borne of false conviction). Those people will almost never participate in a gov or NGO program which includes facilities and monitoring.... And I don't really blame them.
The truth is we need to stop the problem before it starts and the only real way is to prevent traumas, treats those we can't prevent and bring justice against those who use the system to abuse others or protect abusers.
Sadly, in many ways most drug addicts are a "lost cause" before they even start using, just as so many alcoholics are.
That's the consequences of systemic willful ignorance of trauma.