I wonder if HTML5 could be extended to have length, weight, currency and other kinds of tags. Texts would encode distances, weights, etc in the appropriate tags

I wonder if HTML5 could be extended to have length, weight, currency and other kinds of tags. Texts would encode distances, weights, etc in the appropriate tags, with default values equal to the current text. I would then set my browser to "show SI units" and all the "100 miles", "8 feet", etc. would be converted to kilometers, meters, and so on. That would make this article infinitely more pleasurable to read for me.