the problem here is that CSS is _not_ a good abstraction for laying out application. Its good for styling (and i would argue, styling static content too). But css isn't very modular, and has very very high coupling with the structure of the DOM - something that isn't easily discernable at the time of modifying the css.

Like you, i can't think of a good solution - a lot of UI frameworks either just has really heavy restrictions, or it doesn't actually provide enough abstraction to actually help with the problem. Sigh...