well, my post wont be a complete solution, but a possibility to create one.
If you have time, you can define the grammar of CSS in Beyond compare.
and use higher weights on the Selectors and then the Style Elements…
don’t know yet about reordering,
though, Reordering of selectors can sometime be significant change and change the CSS behaviour
Of-course if you have time to create the BC3 Grammar, we would love it!