I have an Astromechanics Canon EF lens mount, so I have come across the same predicament as you did.
I have been looking at two possibilities.
One is to reverse engineer the EAF USB HID protocol, and use a small micro-controller, such as an Adafruit Feather M0 to take HID commands from the ASIAIR and convert them to USB serial commands to the Astromechanics. The Astromechanics serial protocol is well documented.
The second way is to use a ZWO EAF to drive a rotary encoder (I bought a 600 pulse per revolution encoder from Amazon for just $18) , then read the position of the ZWO EAF from the rotary encoder using a similar micro-controller as the previous method, and transfer that position to commands for the Astromechanics.
(Either of these methods should also work with other electronic focusers that are not supported by the ASIAIR, such as the Feather Touch or the Moonlight.)
I am still on the fence whether to go ahead with either scheme since I have not yet decided to even use the Astromechanics with my Sigma 135/1.8 ART (which is really heavy, at over 1 kg), or just use a belt drive from a ZWO EAF (I have a gear ring for the Sigma that is 3D printed for me by deepskydad).
Furthermore, the Astromechanics does not come with a tripod mount, and the third-party tripod mount for this particular lens does not allow rotating the FOV. With the weight of the lens, mounting the OTA assembly using a camera tripod ring from ZWO is not that practical. So, I may end up abandoning the Astromechanics for this purpose, and just use the Starizona EF "LensSlider" -- which has (1) a tripod mount, (2) a filter drawer, and (3) an image rotator -- and using a belt drive from the ZWO EAF to focus the lens.
I have been using a ZWO EAF through a belt drive to my RedCat51 and it works quite well (using a ring gear that was also 3-D printed by deepskydad), so I don't mind belt drives.