I'd love to see that extension. If you write it, I will use it. I use Chrome too, so it should work here.
As to what should and shouldn't be part of the browser -- the way to figure that out is experimentation and competition. When you make technologies and standards simple and easy, people will make independent implementations and try things. The vast majority will be dumb, but some (often unanticipated ones) will turn out to be useful, clever, or brilliant. That's how the technology improves.
When you make standards big and cumbersome, progress stops.
As to what should and shouldn't be part of the browser -- the way to figure that out is experimentation and competition. When you make technologies and standards simple and easy, people will make independent implementations and try things. The vast majority will be dumb, but some (often unanticipated ones) will turn out to be useful, clever, or brilliant. That's how the technology improves.
When you make standards big and cumbersome, progress stops.