Related discussion: Tailwind: Dark Pseudo Class only for Colors
There are indeed a lot of properties that can be independent from either breakpoint or color mode, even more when using Cwicly global colors (with native light/dark variations) and fluid variables, and such switches could really simplify and speed up the workflow.
(With a keyboard shortcut, please 
)
An option would be to keep unlocked the layout options (flex, grid, …) so that even in all breakpoints mode, we can alter layout according to breakpoint, but that might be a little confusing, I admit 