I think that is resolved more or less, I don’t have any problems handling alpha as long as it is premultiplied with the logged color data as I described above.
There’s no reason to add a bunch of gimmicks to make painting more difficult. Using spectral actually makes digital painting easier and simply look a lot nicer. One of these looks less broken and was a lot easier to control the blending, can you guess which is nonlinear sRGB/spectral and which is nonlinear sRGB? 
It’s not just about yellow and blue, it’s about the response when blending blue and white, black and white, blue and black, black and yellow-- everything. It’s just much more natural and easier to work with the colors in this encoding. Dark colors are stronger, light colors are weaker, it feels a lot like the way you’d expect paint to feel without simulated headaches from turpentine exposure.
This is totally possible, maybe just try to jam it at the bottom of the pipeline and maybe it won’t break everything else.