) explains what hexaphonic for pickups actually means. Hexa translates to "six", so your question is basically nonsense.
The correct question would be if you could make an kind of electric "channel" for each string you play (or at least for one string, as this is no digital data at this point and would require extra wiring (and extra frequencies (i.e. "channels" if you transmit it wireless..).
So in that light I don't get it how what you actually want to do with this extra single channel (especially as you usually can't play two string at the same time in all cases without tricks).
Still an interesting question though for other purposes I guess. AD-Converting inside the instrument is technically no problem today (the hardware weight wouldn't be no problem at all even with compression) but OTOH you would limit yourself somewhat.