Very cool! Also quite inspiring.

If you reach limitations using GenericHID, I've been playing with Teensy boards quite a lot over the last eighteen months, I'd be delighted to help with programming stuff like this in teensy-arduino-C. Also Paul (maker of Teensy boards) is very helpful - I got in touch with him re using GenericHID to make custom interface hardware for X-Plane and his reaction was to provide built-in support for X-Plane!