Several have used MAP pulses to signal cyl#1. However, keep in-mind it may be "less-useful" on some setups such as ITBs, which commonly lose most of the MAP signal as throttle increases. This loses the ability to re-sync. That's a separate issue to little signal while cranking, possibly requiring non-cycle-sync start with transition to cycle-sync. I say it that way as that doesn't mean it has to be a sequential setup to use cycle signal.
Alternatively, investigation of other signal sources with a MAP or pressure sensors are still possible, and I have seen modified throttle body signal placement (more of an air velocity detection), crankcase pulse on MAP sensor, and exhaust pulse sensing, for examples. There is a lot to explore, and thanks for your willingness to look at this general option! It would certainly be simpler than poking a hole for a sensor on the valve train or in the case to read a reduction gear.