Sure. You're proposing that we implement a single, golden multi-stream file
format in the kernel.
We could just as well do that in libmultistreamfileformat.so.
But I'll grant that one cannot go adding new metadata to, say, C files this
way. I don't know how useful such a thing is though.
Remember that my main point is that there's a lack of coordination in
userspace. Hell, there's none. Putting it in-kernel forces that
coordination, and may be the way to go, but it's pretty sad.