It would be nice to be able to control several channels at once, something like:
-c 1 -c 2 -c 15

Even better would be range, like:

-c 1-2

or REGEX:

-c [1457]

This may not be practical (not referring to the REGEX part - that's brilliant), since there will be problems fading in/out from current position.
Possibility: Could start fading first from the farthest one from desired position and then when the fading position hits where the others are start fading them too.

Need to have a --invert option to invert the outputs to simplify NPN vs PNP drivers on outputs

From the datasheet:
"The PCA9685 allows staggered LED output on and off times to minimize current
surges. "

Are we doing this? Verify.

Rec 709 formula is being used for duty cycle to adjust brilliance to make it look right when a single channel is given but not when channel is ALLCALL (ie: -c -1)

Duty cycle should be true always. Maybe add option for "brilliance" or "percent" that will be a value 0-1 or 0-100 and will be adjusted by Rec 709 to make it look right to human eyes.

When dimming from 100% to 10% it is fluid, but at the end there's a visual "bounce". It is fairly subtle, but noticeable.

 python PCA9685_PWM.py -a 0x42 -b 1 -s 5 -c 12 -d 100
 python PCA9685_PWM.py -a 0x42 -b 1 -s 5 -c 12 -d 10

On the way down you can see a "bounce". May also exist on the way up but I cannot see it.