....and thirdly (just thought about it) you would confuse the heck out of the pianists: the A would actually sound higher than the Bb which is as confusing as it can get....
Yes. I think some people will think this is nuts, and will wonder what you're talking about at all -- but in a pure sense it is so. Not, of course, in how they sound on the piano
but in a pure sense.
Which, by the way, is actually part of what you had said just before that:
it would be off theoretically
Chopin was into the theory of the music and of the voice leading as much as anybody, I think even including Bach. He wouldn't have been caught dead writing it as an A#, because, in terms of what's going on in the line of that voice, it's not
an A-sharp and can't be an A-sharp.