To make things faster, I think we can just make a LOCKIN which has 3 inputs: it would have one oscillator, but 6 mixers. Should be simple to make.
I think the idea of having multiple inputs in a LOCKIN module is also good for the LSC sensing matrix measurement.
Because right now I am measuring the responses of multiple sensors one by one while exciting a particular DOF by one oscillator.
Moreover in the LSC case the number of sensors, which we have to measure, is enormous (e.g. REFL11I/Q, REFL33I/Q, REFL55I/Q, ... POY11I/Q,...) and indeed it has been a long-time measurement.