For anyone happening across this who is interested, I went back and updated the post which originally spawned this one: Creating a “volume pedal” with nonlinear taper.
The executive summary is: MG3 can indeed be used to remap curves, but other methods can work just as well, including the MIDI Messenger AUv3 and a capable MIDI host device like the H2MIDI Pro. I wound up refining the first two to be functional-enough-for-me, but will move forward with the host device answer as being a more elegant solution.