Yea, that's cute, except that DRM can handle pretty much all of it. You can split hairs and complain about GPU scheduling which is inherently rather difficult because scheduling at the command queue level is problem very much alike the halting problem.
The real issue isn't that we don't have the pieces we need but rather that we can't get all the players to agree on using the same ones. On Windows you have one entity (Microsoft) that can post WLK and unless you pass it you won't be certified and on GNU/Linux "a working driver" can be anything from "not catching on fire on boot" through "actually brings up display" to "oh, hey a textured triangle!".
And I get it, everyone is frustrated because ultimately displaying a bunch of pixels, seems trivial, that is, until you mix in politics. You have NVIDIA, AMD, Intel and the community at large pulling all in different directions. With GNU/Linux graphics support having marginal effect on the bottom line there's little incentive to deal with it. And you'd still miss a controlling entity that could validate that "works on Linux" means anything but "compiles with some random kernel release".<p>Everyone who thinks that writing great graphics drivers can be a spare time activity is delusional.
The fact that we have Android with Gralloc (which in comparison to DRM is, well, a joke), Ubuntu with Mir, others trying out Wayland and folks still stuck on X11 makes this all so much more complicated than it needs to be (and SteamOS is rather terrible in this regard too, which is a shame because Valve is trying to do the right thing with Vulkan but SteamOS is just not a well put together distro, at least right now).
It's just not a driver model problem, it's the politics of it all. Outside of Google adopting DRM instead of Gralloc (or Gralloc getting all of the features on DRM and effectively becoming DRM and replacing it on the desktop) there's probably little chance of unifying all the drivers under one coherent umbrella.