Ballast Resistor
U-L has been reliable, I do use a ballast. If it ever fails I have plan make a trigger module using coil driver IGBT, and active current, like my other ignition use.
Keeping on topic:
I have considered designing and electronic ballast with IGBT and microcontroller. It would be same size as stock ballast, but have many features. It would current limit, properly control dwell, and have auto shutdown for key-On with stalled engine. Those features are in present in my ignitions. Raw parts cost about $10.