Edit by @LeaVerou: CSS WG resolution to work on this, pending a name (options here)

Allow interpolation between both viewport and element breakpoints.

The problems with clamp(), min(), and max() is that you can only interpolate length values on a single property between two points. You may want to interpolate rulesets across multiple breakpoints. You may also want to interpolate things like variable font settings, color, etc. Additionally it would be nice to be able to ease how breakpoints are interpolated as rates at which things scale across different screen or element sizes can often be variable.

Update Dec. 7, 2022

I’ve created an explainer on this issue with a more detailed proposal: https://css.typetura.com/ruleset-interpolation/explainer/

This includes a more specific and detailed proposal as well as a companion proposal to expand scroll timeline. Expanding scroll timeline is likely the easiest solution at the moment but it would make it more user friendly to allow length values as keyframes. This can always be added at a later date though.