It strikes me as an utter waste that nobody has tried integrating the militias.
Give your average prepper a prestigious task involving adventure, physical accomplishment and hierarchy and you are suddenly integrating them. Let 'em carry their rifles along because why not but give them a few radio channels, some mandatory training, mandatory meetings and subsidized gear in exchange for their participation in keeping their fellow citizens safe. Require them to participate with their friends and comrades, give them the slightest bit of oversight (because distrust of the government is clearly a big thing) and not only are you using their powers for good, but you're keeping everyone in contact with each other such that the crazy ones are not only likely to be noted, they're also likely to go less crazy.
"The purpose of a well-armed militia being freely established..." I mean, if we extended the Boy Scouts out to retirement age I think we could solve a lot of problems.