font-size-adjust is the central issue of this thinking process. I agree with Stevie also, I can't see this alone as being workable in current CSS, though I do believe that the article suggested this as a CSS "hack."
The best solution would be (and forgive us if this already exists, we couldn't find it) to give a percentage height to each font, so instead of a CSS segment that used to look like
font-family: Calibri, 'Lucida Grande', Verdana, Arial, Sans-Serif;
One could implement a CSS hack that provides per-font size scaling, a quick and not-too-well-thought-out example being:
font-family: 'Calibri'-120%, 'Lucida Grande'-100%, 'Verdana'-96%, 'Arial'-101%, Sans-Serif;
I just don't see how this could work without causing browsers to throw hairballs.