>| Old-Time PIClisters --
>|     I need your help in developing a new device -- a piezoelectric servo.
>| Remember the crystal (or ceramic) phono cartridge, where, if something
>(like a
>snip

Sounds like piezo actuators. They already exist, for making very small
precise movements.
Coupling anything to your piezo will change it's resonant frequency, and
ruin the "Q" so you won't get the strong movement you see in the unloaded
device.