It's been some time since my last update, I was awaiting some parts in the mail. Those parts were.... *drumroll* radios with LoRa support! It might be reasonably obvious at this point, but the name of the project is play on the name of that modulation scheme. I started with the other radio modules as a PoC, as availability of the LoRa radios was sparse for some time.
First modules I got are the HopeRF RFM95W. They're about 3/4th the size of the RFM69 modules that I put in the original design, and the range should be much improved with LoRa. They fit right on my ESP8266 breakout boards, as the modules are of similar pitch and size. Thanks to this, I'll be able to pop them right on my test boards (with a little rewiring) and I'll be good to go.
Adafruit also sells the Feather board with a Atmel ATMega 32u4 and RFM95W, which is tempting to grab to develop a multi-node test rig.
Secondly, I bought some Microchip RN2903 modules, which fully integrate the radio and break out a UART for communication. They've also got a boatload of GPIO. These might be overkill for this application, but I'm going to run some tests anyway. I'm working on a breakout/testing board for these, which should arrive relatively soon.