Please note that this dB vs. step curve is NOT the dB vs. step curve of the LDRx. We pick points along this curve to build the 70 step audio taper curve that gets programmed into each LDRx with each step being close to ~1 dB. See the last pic for our typical audio taper curve.
I come in peace...and some observations:)
Seeing your curves and your post above, the way I understand it that would be the original 250 steps getting compacted into 70 steps on your final curve? At 1 dB per step all the curves on your pics would now have curves that are very much steeper with less points (70) to connect, right? This would be similar to an analog signal getting digitized with 70 sampling rate...a rather low rate for Nyquist.
And on using LDRs for input switching...wouldn't that be like adding another 100 ohms to your Source's output impedance?
All in all good design albeit very complex.