I like your approach however a person would need to have a much higher level of training to complete your trouble-shooting steps. An Oscilloscope, wow probably not on most guys work benches. He may need to start with some more basic tools and a bit of logic.
Per the manual; NOTE: The following test should be made using MaxiClips and the Fluke Model 77 Multimeter set to DC Volt scale.
This test should be made at the three-pin connector of the regulator/rectifier. NOTE: Test the connector that comes from the engine. 1. Set the meter selector to the DC Voltage position. 2. Connect the red tester lead to the positive battery post; then connect the black tester lead to the negative battery post. 3. With the engine running at 2500-3000 RPM, the meter must show 12-14.5 DC volts. 4. Set the meter selector to the AC Voltage position. 5. Test between the three yellow wires for a total of three tests. 6. With the engine running at 2500-3000 RPM, all wire tests must be within 36-44 volts. NOTE: If tests failed, check all connections, etc., and test again. If no voltage is present, replace the stator assembly. (page 131 in my shop manual, a Fluke-77 can be found on Ebay used)
