I think preppers have done a lot of the footwork with this kind of stuff, especially the conspiracy/militia types.
For example: https://www.survivopedia.com/what-a-ham-radio-is-and-how-experienced-preppers-use-it/
There's some issues though.
You want to privately make communication from your groups radio guy to the HQ, or to one other group. That's fine, you take their public key being broadcast and encrypt the data so that their private can decrypt, but how do you send a message to everyone at once? Sequentially?
What about signals analysis? Is there no way that they could hone in on the strength of the signal and have a direct route to your guerilla camp?
I'd propose that you should have to use a password to access your own radios as well with full ID verif, and a system similar to TCP packets for data transfers as well.
Can we engineer this?