This circuit on page 15 of AN-106 by Analog Devices mentions sub-micron movement. I had browsed this document before during the hectic days of the HaD space race, but somehow I had missed this. The OP-77 is less than half the price of the LTC6090 and there appears to be nothing magical about it, at all.
I'm a little unsure of what the voltage drop across that 2M resistor at the top is supposed to be. - I didn't blow up my uC when I powered the LTC6090 with 24V volts and in a similar strategy sprinked resistors over the high voltage bits. - Instead I get exactly the performance I thought I might get. Together with this circuit I found earlier I have a pretty good refrence on how to do this without the LTC6090.
It is time to move on, and design a test jig to calibrate the movement of the piezo membrane... A laser oscilloscope, perhaps?