Not bad for a non-physicist. I'll bet that there is even a real physicist out there somewhere who might argue along similar lines, but as you rightly point out, the effect is likely to be so infinitessimaly small as to undetectable. Also, it's likely that the quartz crystals would be randomly orientated and as such their piezo voltages would cancel each other out rather than accumulating any field strength.

P.S. Yes, I'm a physicist.