Would it be easier to capture the serial data using your PC between the flight controller and the SR24? That's how I was studying the protocol for developing telemetry for the Thunderbird firmware.. ;-)
You are saying monitor and capture the serial data to the SR24 during a firmware update and then use that captured data as the FW on a zigbee module? I thought about that but wasn't sure that I would be able to determine what part of the serial data was the firmware update and what part was just other communication. But I might have to try that because I can't seem to get a serial bootloader to work on my zigbee module. Even if I could I don't know if the SR24 uses the same type of bootloader.
I don't know, I might put working on programming an off the shelf zigbee module as an SR24 on the back burner for awhile. I did find a thread on another forum where somebody said they had made their own custom firmware for the SR24 that output SBUS. I requested more information, but it is kind of an old post and I haven't heard back yet..