We would love to know more specifics about what kinds of capabilities and scenarios you are looking at. You can leave questions or suggestions on our GitHub page: https://github.com/microsoft/win2d/issues.
For example, there are other excellent libraries out there such as SharpDX - this one in particular exposes basically all of the DirectX API surface. Are there specific things that you would want in a D3D wrapper library?
For a GPU-accelerated math library, are you looking for something similar to existing solutions such as DirectCompute, CUDA, OpenCL, etc?
ANGLE is translating outdated OpenGL ES 2.0 to DirectX...
If you need OpenGL ES 3.0 support in ANGLE I encourage you to reach out to the angleproject maintainers. It's true that 3.0 has been out for a while but 2.0 is still the standard for a large swath of mobile devices in the market.
Who is going to maintain it, provide driver-level compilers for shaders etc?
I'm not sure what your question means here. The ANGLE team @ MS is dedicated to maintaining and improving ANGLE support on Windows over the long term, not including all of the activity around ANGLE in the industry in general. In addition, the main purpose of ANGLE on Windows is to leverage the (well maintained) DirectX runtime, shader-compiler, drivers, etc.