Is it possible for the OP to add an R2LC and a small motherboard? What connections would he need?
Track power Pins 1,2,3,4
Rear light Pins 9,10
Antenna Pin 23
Forward and reverse PWM to Motor driver Pins 16, 18
Most of these connections would be in the existing tether but I suppose the challenge is figuring out the pinouts. I have yet to see any K-line board diagrams online.
Bob