I've been trying to figure out if there is some way to install an aftermarket/standalone/programmable ECU on say a VW with CIS-E, aka, KE-Jetronic. The limiting factor seems to be the lack of a meaningful timing signal. I'm sure someone could configure MS to use the camshaft signal in the distributor, but that signal only comes from a four window hall effect sensor, greatly hindering accuracy of the ignition system. The rules expressly prohibit crankfire ignition systems, but what about "camfire" ignition systems?

So I'm wondering, would it be allowed to replace the four window hall effect sensor with say a mini 36tooth wheel? And replace the hall effect sensor with a sensor that would read the toothed wheel? The rules say this on the subject:
"Any ignition system which utilizes the original distributor for
spark timing and distribution is permitted. Internal distributor
components and distributor cap may be substituted.
"
I suppose the intent of the rules was that the distributor could be replaced with one of similar function but from a different supplier, like Meyle and Febi parts for example. But the rule does expressly say the "Internal distributor components.... may be substituted." The function of say a mini 36tooth trigger wheel is similar to the function of the four-window vane inside the distributor. And the function of an inductive sensor is equivalent to that of a hall effect sensor. The signals are functionally equivalent, it's just that one has a lot more resolution and a gap at TDC, but otherwise the signals are the same in that they are just pulses read by the ECU.

I realize that the camshaft rotates at half speed, so a 36 tooth camshaft wheel is equivalent to an 18tooth crankshaft wheel, and there are physical limits to how small a toothed wheel could be made and still have the inductive sensor read the gaps.

I'm sure it is prohibited due to some flaw in my logic because I'm prone to creative interpretation of the rules. But I'm wondering why not so I'm throwing this out there for the discussion.