Personally, I like the Chopinism of this movement Henry. (If that's even a word!)
Also prefer it to the other movements, mainly because I can actually play this one! (Due to the slower tempo.)
That said, the runs are quite challenging for me (as a very rusty pianist).
I wonder why you see the pentatonic as purified Locrian? Seems like an original and interesting idea!
Ofcourse Locrian is notoriously difficult to write in, since the tonic triad is a diminished 7th, and therefore sounds unresolved.