It seems to me that the best thing for HTML would not be to add a bunch of new features based on current design, but to add lower-level primitives that can be u

It seems to me that the best thing for HTML would not be to add a bunch of new features based on current design, but to add lower-level primitives that can be used to do the same thing efficiently. If the web was based on GDI code instead of HTML, then we wouldn't even be having this discussion. You could do anything you wanted in terms of design. I'm not saying the web should be based on GDI, I'm saying given designers low-level access may be better than adding high level features.