Hi,
I’m a 3D animator. I use the opensource software Blender. As you might know it is possible in 3D software to link a joystick or a mouse to the input of the motion. That makes it possible to record joystick or mouse movement to the motion track. You’re kind of puppetering your characters motion with the joystick input.
Now here’s my question: Could someone make a kit like this:
A skeleton consisting out of bones -> metal joints that have rotational sensors and that transmit only during rotation coordinates. It’s should be mecano style skeleton. The animator can first construct it’s skeleton and then move and record the joystick input of the arms then the head etc?
When the movement is finished there skeleton should not submit any rotational data. Only when moving relative motion could be recorded.
An animator can build it’s own skeleton and move the skeleton -> only the upper body makes sense -> to control it’s motion and record it to the motion curves. It should act like a joystick and only transmit rotation coordinates relative. This shouldn’t be that hard to make. If someone could make one for me at a reasonable price point, I’ll buy one. There is a small market for this kind of devices. I’ll be thankfull. 
The most cost effective thing for you to do would be for you to make your own (you know best what you are looking for). You could start with joystick pots/components placed at the joints of your skeleton, and then get/make a computer program to record the inputs from the components as the skeleton parts are moved (the movements would appear as joystick inputs).