Yes, and this is the princept behind the Extensible Web Manifesto. I get it. I'm pushing for that same stuff, too.
My point is, we're starting to let the fact that we've done that first part (or even that we could do that first part) stop ourselves from doing that second part, where "The browsers can then adopt this as native behaviour if there is enough user interest in using it." (Or, if we're not having that problem yet, without keeping vigilant on this point, we're going to, because this is the natural apathy that all DIY ecosystems trend toward as their thought leaders move higher and higher up a stack of pre-built specifics they're comfortable with.)
As an analogy:
Say some young idealists open up a free public workshop in the local community. They don't have many tools - just a hacksaw, a hammer, a screwdriver, and a blowtorch. Every now and then, in the early days, they realize they don't have something important, like a pair of tongs, so they go to W3sley's Hardware down the block and buy one.
But, as the shop goes on, it becomes increasingly self-reliant. Rather than go out to the hardware store to buy a new clamp, the staffers build one by shaping a couple pieces of scrap iron with the blowtorch and chiseling grooves by hitting the screwdriver with the hammer. Sure, it's heavy, and sometimes you cut yourself on a rough groove, but it has this neat ratcheting behavior that you couldn't get with one of those clamps they would have sold you at the store. Eventually, all the tools the workshop uses are being built like this.
But then a funny thing happens: new people stop coming to the shop, because when they walk in the door, they get hit in the face with flying cinders as the regulars snark "looks like somebody doesn't know not to stand under the Gruntacetymalizer duct!" They ask where they can get a dremel, and the person behind the counter rolls their eyes and says "People keep trying to give us dremels. You don't need a dremel. We built a handheld circular saw ages ago, it's basically the same thing and it works fine." The new prospect takes a look at the circular saw behind the counter, sees the burnt holes in the plastic and the blood still wet on the blade from the last new customer to tear their arm off trying to use it, and says "uh, OK, thanks, but I think I'm going to go. Now."
After seeing how bad things are at the community workshop, they head out and buy a dremel from the hardware store. Rather that go to W3sley's (which went out of business years ago after the workshop staffers stopped shopping there), they get the dremel from their local corporate iDepot, which charges them $300 for the tool and requires a $50 subscription every year to sell the things they build using it, and states that it's a breach of contract to buy plastic from any other hardware store - but it's still better than going back to the spiky, decaying madhouse that is their local workshop.
Years later, the workshop blows up in a freak accident as their most experienced staffer was busy cutting a second nozzle into the Gruntacetymalizer's fuel tank. At the wake, a few young idealists, who never really went to the community workshop all that much, gather around the circle and talk about some of the cool things they heard this place used to do. As they talk, they grow increasingly enamored with these romantic notions, and they complain about how creepy the iDepot is and how much they over-charge for tools, and then one of them gets a clever idea:
"Hey, we should open up a free public workshop!"