You are correct, I need to use something like the CPC1025 instead of the AQS221.
Every other cell measured will reverse polarity so I need to rectify the cell voltage.
The top half of the OP with the diode forms an ideal diode.
For a positive-going input signal, the bottom opamp can only function as a unity gain buffer, since both inputs are driven positive.
For a negative-going input signal, The ideal diode prevents the non-inverting input from being pulled below zero volts. The bottom opamp will then functions as a unity gain inverting buffer, with the inverting input maintained at zero volts by the feedback loop.
Input impedance is non-linear, having an almost infinite impedance for positive half-cycles, and some 50K input impedance for negative half-cycles, so I need U71 to drive it.