@jakob - that's a great idea and something I have been tinkering with. When you say "not a secondary corrector (...) but a way to protect and optimize skin tones" the first thing that comes to mind is color range masking. Masking would allow for the exclusion of certain color ranges from the grade. The mask could be applied at different intensities to the Hue, Saturation and Luminance color channels to create a more natural exclusion.

For example: You would select skin tones based on hue, saturation and luminance ranges. Instead of just cutting out the selected skin tones from the grade entirely (which would look pretty bad) you can selectively blend 50% of the original skin hue, 100% of the original skin saturation but keep all of the luminance from the color grade. To keep the feature versatile, color range selection would not just be limited to skin tones.

Would this be a step in the right direction of what you had in mind?

Yes that sounds right. Basically a way to avoid overly agressive skin tones when creating different looks. It would make sense to include skin tone optimising options like hue compression and other ways to target natural skin tones.

The latest update introduces new color range isolation and tone compression tools in color.io: https://color.io/user-guide/color-grading-tools#mask-compress

This is an exciting upgrade