After some more experimenting, I'd like to request an update if it's possible:

Can this plugin be changed so that it only adjusts the mids in the RGB gamma curves, (around 128) and leaves black and white levels alone? That way it might put out a much better result in some cases, and I think it would prevent luma flickering if using it to match two video clips?

EDIT:

I don't know if what I mentioned there would be the cure but you see, the problem I'm having is for example: A bright scene with lots of bright whites, a dark object passes by but never covers the whole screen, yet the output video gets darker when the object passes by.

Maybe it's because this plugin calculates the average luma of the whole image? At least that's what I think it does?

Maybe it should be based on calculating luma not by average but by black and white levels, no matter where in the image they are? Or by mids like I said before.

No idea what would work best, but I'd love to see a fix for this.