Joking aside, the LS "knows" when the sustain pedal is held down, it also knows the current "position" of each sensor at the time the sustain pedal was held down.
If we were going to handle Z affecting volume, then we could say that only increases in the Z value would have any effect until the sustain was released, decreases would be ignored in this time period, including the note off triggering. When sustain is released all the missing note offs would be sent.
A new touch (note on) when sustain is held would either add a new sustained note or reset that existing sensors sustain handling .
There is the problem that when sustain is released the remaining held Z values could be the same, or most likely less. So I guess the current value could be latched until note off, or be slewed over time to the current value.
Handling Y is a bit more problematic I guess, but a simple solution would be to treat it the same as Z. Or maybe just ignore any Y changes after sustain is held?
It's quite interesting really, would actually be quite a neat thing to have.
p.s. Had a few beers, probably talking rubbish