Mostly just to add my own scepticism to Alexandre's, but also for the record (I don't think that was a public conversation): If it's in fact worth the effort to define some kind of sensible API (and I'm not sure wined3dx_get_image_info() from this MR qualifies...), we might as well make that API available as part of vkd3d, along the lines of something like vkd3d-utils.
It also seems tempting to just use the existing d3dx API for this, possibly with a couple of versioned variants of some exports. The number of instances of D3DX_SDK_VERSION/D3DX10_SDK_VERSION/D3DX11_SDK_VERSION seems rather limited, and mostly confined to the effects framework. The bulk of that code is already within the scope of libvkd3d-shader. The number of instances of D3D_COMPILER_VERSION is slightly larger, but d3dcompiler as a whole is also already within the scope of libvkd3d-shader.