surely you could just have a switch on the clutch conected to the resistor pack that is only armed after say 50km/h (or maybe arm it only when the revs go above say 6000)
then it just cuts spark when you hit the clutch (might even works as anti lag with all the fuel flowing out the zorst)
im sure its not good for it but seems very simple to do
dont know why you would want it on a road car though