Have you found a good solution for this?
Yes! For my current use - Sylphyo => Link/MIDI => Cantabile => Kontakt 6 - the facilities for drawing response curves has been the complete solution for handling this issue. This was suggested and discussed in detail in this thread on the Native Instruments forum:
... and I have found that the flexible envelopes (drawn, rather than the table option) are a straightforward and complete solution. I have recently been using envelopes for other purposes - controlling parameters on modular synths using elevation and roll (have not tried compass yet) and that is a fantastic alternative to expression pedals.
For other scenarios that do not have the flexibility provided by Kontakt, I am not sure the solution. MIDI filters do not seem to be the answer, since they are translating MIDI to MIDI, not extending the bit depth of the MIDI stream itself.
There might also be an issues for sound libraries that are encrypted (locked) by the vendor, rendering the curve inaccessible - but I'm not sure about that.
... and Thank You @join for the amazing amount of detailed information!