I think the ‘single CDI channel’ thing is a non issue if the current ignition setup is working on the target engine. While I suspect that one would likely get an increase in efficiency coupling the EFI to the CDI, I think that efficiency increase would be relatively small compared to what is gained by converting from carbs to EFI.
Lessons I have learned the hard way from years of mistakes include the classic, ‘if it ain’t broken, don’t fix it’.
I greatly suspect that the electronics of the EFI system adjust much faster than the mechanical advances of the stock ignition, so optimizing fuel alone shouldn’t be too much of an issue.
That’s just a guess as I’m evolving my boomer brain to new ideas.
For example, the wasted spark EFI on my bike works just fine. It has a mechanical advance, a couple of hall effect sensors on the crank, two dual lead coils and two (what they call) spark units. Pretty much as bullet proof as it gets.
It gets two (one each) pulses from the hall sensors per revolution, one (or maybe both) might work as an EFI trigger if the advance doesn’t mess with the fueling.
If the advance would screw up fueling, then adding a crank position sensor shouldn’t be very difficult.
I imagine it would work about the same for Bodie’s VW aircraft engine.