Would love to see something that conforms properly to the WAI Authoring practices and supports microformats2. That could combine well with a stylesheet that doesn’t use any custom classes, just microformats classes and role attribute selectors.
My current site doesn’t actually use any classes in the CSS apart from image-rendering utility classes; I use POSH, ARIA and microformats selectors for everything else.
The great thing about a purely semantic stylesheet is re-usability across other websites.