after avidly devouring your thread on this subject i started looking into doing one for my self and through all the reading, maybe I missed it and you can correct me if I'm wrong the stator laminates of the bpm are said to be 0.5mm.
I may have found another version of the bpm that claims 0.35mm lams and curved magnets on alibaba unless they are lying here is the link anyway Im currently communicating with the seller about getting one sent to australia for conversion on my FS bike i was looking at an rc drive but this modification of a hub is so much simpler.
here is the alibaba link https://www.alibaba.com/product-detail/ ... c049j33pPo
another thought i had is about the failure of the nylon gears, i suspect this is likely from high power levels being applied when the nylon is too hot. have you played with the replacement steel gears that are available ?
and I love your idea of using one of these for an epicyclic variable ratio transmission that you mention in another thread
current ride is a 1000w rc motor friction drive using a vesc.