The CDI can be used on any engine even on a 4 cilinder.....with a little help of a electronic/mechanic switch.
It doesn't matter if you generate a spark in the exhaustrotation, the petrol is all ready be burned.
You can also use a counter IC (CD4017) or flipflop who release the spark every second count.

I don't understand a coilsensor ?
A CDI need a exact ignitionpoint to spark, it's much faster then a normal pointswitch.
You can also use a opto-sensor with a black/white disk or a hole into a white the disk.
Something like this, only with one white line