The pink wire from the ECM Tach output pin to the cruise module is so that the cruise module can detect engine overspeed - a condition that will auto cancel the cruise control via a reed switch.
To put in electronic cruise you would need the electronic cruise control module, the stepper motor/throttle activation, the handle bar controls/throttle/front brake, switches for the rear brake and clutch ....... retrofit all from a bagger.
I think the hardware would be messy unless someone sells it as a kit.