I would love to see such tools have some accessibility DX built-in. The idea is to define the color palette in such a way that we know whether a color combination is accessible just by looking at the color name. For example, using the USWDS design system, I know that blue-30 on gray-80 is accessible (WCAG AA), because the difference between both values is 50+. I once wrote a blog post about this (niche) concept: http…
You identified the concept as niche, but I would argue this should be a first-class priority in web design. We will all be disabled at some point, permanently or temporarily. So many great tools are unusable due to accessibility reasons (like Streamlit!).
For example, #F00 text on an #000 background passes WCAG AA, but will be unreadable for users with a common form of color blindness: https://accessibility.psu.edu/color/colorvisiondetails/