I wouldn't hold you breath. I understand what you say you want to do, but that is going in exactly the opposite direction that the industry is moving.
Using MS's cloud based sync is not an "extra step". It reduces the effort to keep things synchronized on your part to nearly zero.
If there is no 'trust issue' there, as you seem to imply, then it seems you are simply trying to complicate your life by refusing to use the application the way it was designed to be used.
One Note isn't anywhere near being 'one of a kind'. It's one among many, and not a very good one at. It's bloated, slow, and cumbersome.
Investigate other options, or use it the way it's meant to be used, but hoping that Microsoft will move in the direction you want to go is pretty much pointless.
Tools like File Explorer can often do more harm than good. you were never intended to have access to the file system on the phone. One wrong move can really screw things up.