Make a list of HAMs who are announcing AMPRnet prefixes along with their locations and their contact info. Put it on the ampr.org portal so everybody can access it. That would be more formalized without being needlessly centralized.
I think this is a good idea that should require little effort for Chis G1FEF to implement.
When you are looking at your regional networks it could show if they are BGP or IPEncap connected. That flag is already there, and the means to be able to message those folks via the portal appears to be there.