I think we really need a minimal format for binary shaders (I really mean minimal). I wonder if mesa with ACO has one. GPU is all about performance, optimized assembly is more than appropriate. Still could have a reference implementation authored directly in SPIR-V (text->binary SPIR-V with a ssa checker), to avoid pulling those abominations of glsl or hlsl compilers (unless it exists plain and simple C written glsl or hlsl compilers to SPIR-V).
This web site is really good, reaaaaaaally good.