Ok so any system needs a cam sensor to run sequential. It is the only way to determine overlap vs power stroke. Missing tooth trigger wheels will not take the place of cam sensor. You could weld on to the front of the valve cover and mount a sensor to read off a tab off the cam gear or weld on a tab to the washer in front. You will need to have this timed to the degrees or number of teeth from the gap in the crank sensor.
There is not a huge reason though to run sequential vs wasted spark. The engine will run smooth and have good power without. It is mostly an emissions issue.