I've been trying to wrap my head around using COLLADA for multitexturing (bullet decal on a wall for example). I've been reading the 1.4 spec for a while and it really seems bizarre. This is what I've gathered so far from my reading and searching, maybe someone can correct me if I'm wrong.

1) Its impossible to use multiple diffuse textures under the 'profile_COMMON', so either profile_GLSL or profile_CG have to be used.
2) In these profiles, there's no way to simply describe a texture blend operation? From the code samples I've seen, it looks like you're expected to actually stamp the entire GLSL shader into the collada file, which seems ridiculous to me. This would be practically impossible to parse, so if you want to do multitexturing you must use the shader in the file as is? What if I have ten different collada models that use 'the same shader' effectively, but each one has a syntactically different <code> block? I have to keep around a separate shader for each model? What if I want to use a DirectX codepath?

I got the impression that collada was supposed to be the common format of the future, but this seems really onerous to use, I just don't get it. Surely there must be a simpler way to perform texture layering?