Have the browser make a shallow copy of the DOM and allow developers to manipulate the shallow copy. Then have a update() function that will take care finding the diffs and update the actual DOM. Seems like it would be much faster than a javascript implementation also.
Funny, after years of Win32 C++, VB, and then web development, I find I can slap together an interface so much faster and better-looking using HTML/CSS/JS than anything for the desktop.
However, "slap together" may be the important phrase -- putting together a well-architected, consistent, extendable, etc. interface is perhaps a little hairier. But the DOM is great for building UI's quickly, with trivially easy custom styling and graceful resizing.
I'm the real programmer.
And to the downvoters: My apologies for the offending you. I was simply trying to point out that the grandparent post is not comparing apples to apples, since it's very likely that he's achieving "fast" web development because he's either developing trivial user interfaces (i.e. not using anything that would require a layout manager, not required to support older browsers, etc.) or because he's using lots of other technologies in addition to the DOM (third-party javascript libraries, like jQuery, for example.)