We are not pleasant in terms of OSX. The user share doesn't mean much to a community driven project, the developer share does. Sadly, there seems to be no developer here how cares about OSX. Everyone focus on his own setup. If you just hate windows, you can also try linux via bootcamp 
Of course, writing and maintaining a metal backend will be nice. Try to fork the null video backend and add new functionallity (in this order):
- window + context creation + presentation (Render.cpp)
- vertex buffer management + draw calls (VertexManager.cpp)
- shader compilation + caches (ShaderCache.cpp)
This should already give you regonise-able rendering in a few games.
Of course, writing and maintaining a metal backend will be nice. Try to fork the null video backend and add new functionallity (in this order):
- window + context creation + presentation (Render.cpp)
- vertex buffer management + draw calls (VertexManager.cpp)
- shader compilation + caches (ShaderCache.cpp)
This should already give you regonise-able rendering in a few games.