If you put it this way - discussing possibilities - then yes, it is possible.
The camera updates firmware in all other modules by sending DUML commands to them:
- enter bootloader mode
- start firmware binary transfer
- send binary firmware chunk (repeated until whole firmware is sent)
- confirm uploaded firmware validity
- store the new firmware
So - all you need to do is to capture the communication between modules, learn details about the protocol and write your own firmware updater which would send the DUML commands via virtual serial port which you get after connecting the USB cable.
Or you can reverse-engineer camera firmware and get the detailed update procedure from there.