Here is a potentially cool controller idea. It has three capacitive sensors arranged as the corner of a cube to track your hand on 3 axes. It would need some modification to get three neat CV outputs, but it could potentially fit in a module or external box.
The sensors could be made to fold down for quick and easy deployment and storage.
Super cheap and easy to make. Just an arduino, 6 resistors and some kitchen foil.
It's basically a 3D theremin. Imagine having two of them and 'conducting' your synth?