I like your way of looking at it. Here's another way: techncially
speaking HTML already supports charts. The IMG and FIG attributes could
easily point to an Excel or Harvard Graphics chart file. The real problem
is not in HTML, it is in the non-existance of a widely used chart
data format. The best place to attack the problem, then, is to standardized
a separate chart data type independant of the HTML standard and get
browser vendors to support it. While you are at it you might want
to standardize a vector drawing format.
cil.org is struggling with the same questions of format standardization.
w3.org might want to work with them to address these issues. Or the
cil.org formats might become defacto cross-platform standards.