I wonder if native D3D would really help at all. Most OpenGL drivers in Mesa are really Gallium drivers. Gallium is a low level internal Mesa API uses to implement support for higher level APIs, including OpenGL and Direct3D 9. Vulkan support isn't implemented on top of Gallium, because Vulkan is apparently lower level than Gallium is. These drivers are still pretty damn fast, despite having to go through and intermediate API. If Gallium is fast enough for OpenGL drivers, I don't see why the lower level Vulkan can't be fast enough for Direct3D drivers. As far as I'm aware, the performance difference between DXVK/VKD3D and Direct3D drivers on Windows is already negligible.