It's a model that's been pretty widely used.
I'd make a distinction here between civilianization and what is typically referred to as tiered policing, which refers to engaging individuals to carry out different and often more basic functions than what a typical police officer would do. Let's take, for example, the U.K., where they have a fairly robust tiered policing framework in place: there are the sworn police officers, who are the majority of the staff; there is the civilian staff within the police service, who often carry out administrative and support functions; and then there are two other categories of police personnel.
The first is what they call police community safety officers. These are individuals who are very engaged in the neighbourhood and the community—understanding their needs, gathering information, and working to solve problems. That is one other level.
The other one is exactly the one you referred to, which is volunteers. They call them special constables in the U.K. We have them in Canada, too. Different police services use them to varying degrees, but they can often be a very helpful resource for meeting policing needs and meeting the needs of the communities in terms of visibility and some of the more basic functions you don't necessarily want to have a fully sworn officer carrying out.