Hi, Implementing Direct3D at driver level won't magically fix things. The issues will be still the same: Undocumented or incorrectly documented behavior of Direct3D and broken apps which rely on defined results in per se undefined situations. There are only a handful of cases where OpenGL<->Direct3D differences make problems, like non power of two textures or flat shading. Those could as well be fixed with proposing an additional extension, instead of turning everything upside down in Linux(and at the same time MacOS, Solaris, *BSD).
Hardware doesn't magically execute Direct3D 1:1. In fact, Windows drivers essentially do the same: Map D3D to a hardware interface which is a hybrid of OpenGL and D3D. You can see this by looking at nvidia extensions: They have a GL extension for almost every single bit of d3d functionality that does not map 1:1 to gl.