It is a useful request and given the hardwired mod matrix, it will be of very limited use. Personally, I can see the appeal of per channel/voice pitch (X) and AT (Z) for filter cut-off and that would be as far as you could go with OB-X8 if it was able to interpret MPE MIDI.
For the rest, synths with a flexible mod matrix (eg Hydrasynth, 3rd Wave) will be a better fit for this special purpose. Unfortunately, the Prophet 12, which also comes with such a mod matrix, would benefit the most from MPE but it is no longer supported. Hopefully, Sequential will one day fill this void.