Thanks - you can pretty much take any class-based grid system and use them this way in LESS (and SASS, of course).
(And if you're rolling your own, you can even be more concise - such as, instead of invoking theWidth() twelve times to build your classes as shown here, make an atGridColumn() function and skip making those classes.)
Indeed. Sass and Compass have been doing this for years. Using mixins for CSS framework rules so markup stays semantic is basically the core concept behind Compass.