I'd rather the protocol gets updated so the crypto key can stay on the phone.
I think we're a bit past the initial AES issues, at least the Meshtastic project promptly alerted people to their crypto issues and encouraged everyone to update firmware asap.
It's not too hard to use, as long as the hardware is flashed and ready. For the end user, it's an app that connects to a bluetooth connection. I think it would very trivial to have a few good LoRaWAN ops in the community, flashing nodes en masse and handing them out to peers.
With the "cell phone + companion radio" setup which is currently very popular, it would seem the correct solution is to perform encryption on the phone – using the Signal protocol – and use the companion radio only to send/receive these blobs.
This has the added benefit that you can pair with _any_ arbitrary companion radio, rather than your identity being tied to one specific radio you own.