I think is good idea to be start this kind of project. It will make easier to port games/apps from windows to linux,mac and any other os that support vulkan.
I hope someone will contact with valve, wine and sdl guys and share this idea. I also hope that the community will hug this idea and start the project itself.
For regret im not very experienced in 3d programing and can't start this project as stand alone.
pros:
1 open source
2 user space
3 os independent
4 vendor independent
5 widly available
6 give access to d3d9 renderer to our favorite os
cons:
1 require d3d10/opengl 3.3 hardware

fill free to share your opinion.