Alternate Input API
My work involves a lot of non-traditional input devices. From gamepads to custom industrial controllers. Being able to develop middleware on my end and communicate with, let's say, a websocket API into XD would allow for much wider usage at our studio.
Ex. Websockets, UDP or TCP to control prototype interaction.
Palette Info commented
Austin, this is a great suggestion and exactly what we at Palette would use to enable a controller integration. Consider it seconded :)