Will have to get back to you sometime this week - family took more time than anticipated. But, I can layout a few things:

jackboots with a yagi will show up and arrest you.

Yeah. This is why I recommend avoiding it altogether. Regulatory agencies are too on top of the licensed spectrum when just worrying about keeping HAMs and others in line. The tools to catch unlicensed operators are just too well-developed and proven to consider it practical for a transport layer, outside of things like natural disaster and the like where transmission in the clear isn’t usually a concern.

If more end-user hardware - or even a non-RF medium - would work, great, no issue. Like you said, there’s no way to support too many assuming they’re safe.

Exactly. If you’re using RF as a physical layer, low-power in parts of the spectrum where encryption is both allowed and common is what you want.

Yeah, so a hub just makes good sense - with such a modest network capacity relative to hardware capabilities, why not gather as much in one place as possible? Because one hub might get busted or just fall to some version of enshittification, it should be easy enough for a user to switch, but I think it’s the best choice of central organising principle.

This is where IP may come in handy for Layer 3 (I’ll come back to that).

Other than anonymity, is there a reason to separate out spokes from endpoints? One thing I already have worked out is a system where the hub can keep track of who has helped transmit things (in a cheat proof way), and could simply give credit for traffic moved, offsetting whatever cost there is to use it (ISPs aren’t usually free to start with, and this one is a safety risk to operate). The bandwidth overhead is literally just a key ID (address) and a hash per hop.

No. I think you are right. Spokes and endpoints should be indistinguishable from the outside. There are a number of mechanisms that could be used but, one that comes to mind would be having the packets wrapped in encryption that is decryptable only by the intended receiver, and having the final “hop” as part of the encrypted packet header. That would bring up some funky cryptography needs that is have to dwell on a bit.

A spoke could literally be servers connected via a “regular” network between hubs, a BLE or LoRA data transmitter, a USB stick, etc. As long as the L2-3 is supported in the stack, it should work.

I don’t really have anything to add there. Proving identity beyond just “I hold this key” is out of the scope of what I was considering. I’d probably go about it the same way I would over a more traditional network, if it came up.

Might look into PGP/GPG. It could be a useful approach. Essentially, the idea being to be able to not take someone’s word for who they are but rely on a consensus of trusted parties. Like PKI but not as centralized.

Edit: Oh, and I’m not really sure how well this all dovetails into IP. If it can, that’s great, of course.

I really think it can pretty well. Using IP would give a native way to route on traditional networks and make traffic more likely to blend in with existing traffic. Building a protocol on Layer 4 reduces the implementation overhead by taking advantage of existing abstractions. Layer 3 doesn’t need to know anything about the layers above it or below it, it just needs to know which server is sending, which server is receiving, and the payload.