We're working on a new default template and had some ideas about improving the CSS handling before, so it might be a good idea to include a more powerful CSS preprocessor.
seems to be the current tool of choice.
A PHP implementation is available at https://github.com/leafo/lessphp
- it seems clean and easy to integrate.
Adding a semantic grid framework as described in http://coding.smashingmagazine.com/2011/08/23/the-semantic-grid-system-page-layout-for-tomorrow/
could ease the creation of modern, responsive templates even more.