To summarize my findings ...
1) There is absolutely no increase in noise (72V) with the metal gear in the Bafang. My Bafang is still more quiet than my Direct Drive hub motors (but it will never be faster). My only issue is the single metal gear I have has no bearing. If I could get the metal gears with bearings (at under $15 each) I would be selling the Bafangs right now.
2) I tested the sensor-less module on the Bafang. It works fine AND from a dead stop. It also works WITH the hall sensors connected. The (Keywin) sensor-less module is designed to spin a BLDC (rotor) in only one direction. The only issue with the sensor-less module is the "jitter" at low rpm when BEMF from the phase wires is low. In a geared motor this effect should be reduced. Testing is (of course) needed to prove this is the case. Same applies to the PUMA and BMC geared motors with the sensor-less module Infineon mod.
3) The Bafang at 72V just barely does 30 MPH (26" wheel). 30 MPH is my benchmark for performance. The torque at start-up is phenomenal, however, and the motor stays cool.
4) I hate thin phase wires. Hate Hate Hate Them. If eliminating the hall sensors and beefing up the phase wire gauge works then it is a winner. The only issue would be starting from a dead stop while on a step uphill incline. This could still cause jitter even on a geared motor with the sensor-less module.
So who will be first to step up to the plate and provide metal gears with bearings for the Bafang?
Now this is not the end.
It is not even the beginning of the end.
But it is, perhaps, the end of the beginning.