Thanks, yes...we will have a FET switch in series with that battery (not shown in top post) , and if its voltage goes too high, we'll switch it out.
Do you think maybe we'll need to connect inputs and output of the OTA together, then apply the control voltage to that? (instead of the way we've done it in the top post)?
After all, if inputs of OTA are the same, then its output current is zero...and so its output impedance must then be highest, which is probably good for our situation where we want to "Inflict" an external voltage onto the OTA output? (in order to control the power throughput of the Boost PFC stage)