Maybe it would make sense to write a plugin for FreePIE that would expose the virtual controllers? For example, the body and hand positions could be read from Kinect and the buttons, analog pad and/or controller rotations could be read from FreePIE.
Given that many requests for features mention various controllers and adding each of them requires writing specific code, such plugin would work quite well before such specific support is added. The additional benefit would be that various combinations of controllers could be used without much hassle. For example, TrackIR and Wiimote are already recognized by FreePIE.