Something like this was proposed in the recent I18N draft (see html-wg
archives. Sorry: no time to give a URL).
It's a reasonable idea.
> Some of the
>more archaic units like "grains" used in medicine and when
>specifying bullet weights will be harder to do, but nothing beyond
>the collective genius of the HTML working group... ;-)
In fact, the HTML WG was _unable_ to come to consensus on this issue,
basically because there isn't much in the way of implementation
experience to draw from. It's not clear how much of the problem
you have to solve in order to make it worth doing, for example.
So I'd encourage folks to hack something up, prepare some information
using the hack, and report back to us on how well it worked and how
well it was accepted.