Many years ago I ordered from ETCO the internal guts to this unit. The product detail from ETCO even said "Panasonic Quad Joystick". It had 4 rather crude & cheap looking un-sealed carbon comp pots mounted to control X/Y levels in a rather clever mechanical arrangement. That means your decode audio signal would have to travel all the way to and from the balancer in cable of dubious quality with possible crosstalk added & depending on the cable capacitance maybe some loss in the treble. I did find use for the quad joystick balancer but not for music.
All tho wired remotes are a pain, I really liked the way the remote on the Fosgate Tate II functioned. Just DC control voltages in the wire, no audio signal. And I thought it was sensible arrangement of L/R & F/B & volume layout that was easy to tweak to perfection.