Independent Saturation tool

Make a Saturation tool that works independetly of the Exposure tool, and that works POST color grading (for example when changing color with the Chanel's levels, or Curve's levels or both the color editor and balance tool). so as if I want to modify saturation AFTER grading y color, and maybe desaturate completely (to then use a mask luminance to apply it only to shadows or highlights, for instance) it properly desaturates and not into a chromatic dominant.

Also this tool could work in different color models, such as HSV or HSL, for example, to achieve what some call "substractive" saturation.

And top notch would be if also you could determine different amounts of corresponding luminance to RGB when desaturating. Like different ponderations of the corresponding gray tone for a Red, Green or Blue channels (and not a default ponderation based on a standardized recomendation like sRGB or Rec709)