Game Player needs to honor controller configuration devicedata.
Game Player, while it does put a custom controller in place if one is present in a Joystick device template, it does not re-map Orbiter appopriately (so the orbiter buttons stop working for some things.)...
The solution is to add code to parse the controller file. This will be a simple parser (it will not catch all possibilities currently, I am implementing just enough for the X-Arcade Tankstick at the moment)