A while back when I was using an asiair pro with a HEQ5, I modified the asiair to use an 8bitdo M30 to control the mount and EAF. Simply turn on bluetooth on the asiair OS and pair to the gamepad, install python3, pip and evdev. Write a python script to read the gamepad buttons through evdev and setup a service to run it and setup some udev rules to call the service when the gamepad is connected. The python script then uses indi to control the mount and EAF. Easy.
I would suspect the AM3 is being controlled through INDI or ASCOM and not directly, so don't worry, your proprietary protocol is safe.