I'm pretty sure the, 'hand-crafted-web' look is going to require deep CSS and HTML diving anyway you slice it.
I haven't touched WP in a few years; does it have the equivalent of the Rails Asset Pipeline yet?
As for the per-post CSS files it would be easy to do with a Posts custom field. You could take text input (CSS) and spit it out in the header using a basic query on the current post.
*This plugin hasn't been updated in over 2 years. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.
http://wordpress.org/extend/plugins/per-post-scripts-and-sty...