Interesting thread... good to see that a solution was ultimately available.
What an interesting design choice, though. It's kind of half-assed, really.
If I were designing this, I would have designed into the mount a powered USB 3.0 hub, then take an internal USB connection for the USB-serial connection of the mount controller. Then they'd be left with 3 USB ports that can be set aside as USB sockets on the control panel to connect other devices to. Or they could create a second hub to provide a total of 6 USB sockets.