Mapping between Currier A and B

[nablator]

But maybe I am being too pessimistic. Suggestions for specific features that look mappable are welcome.

The inescapable conclusion for me, even without trying, is that mapping from Currier-A to Currier-B is impossible, because of the fluid nature of Voynichese, continuously (and sometimes discontinuously) drifting. This evolution cannot be ascribed to a set of rigid rules. As you said: no hard rules only preferences.