This is a good idea and one I have done a bit-- IMO, it is the best of both worlds, though I hadn't thought of using a silent class (did not know there were silent classes, in fact).
Personally, if I am working quickly, I like having what amounts to a grid api exposed to my html and use it a lot, but I agree that it is better if it doesn't have to be baked into the markup.
What about creating silent classes for the column sizes you use and `@extend`ing those classes?