From the proposal:
USD is not 'just a 3d format'. Its scope is far bigger and more comparable to an entire game-engine project rather than a single asset. It can make use of FBX files, and it could make use of this proposed format in the same way. USD does not replace FBX, or any other file format like that, and it's very complex.
I don't want to bash on USD, but its use is mostly in the VFX world, which vastly differs from game-dev.
Also, last month, I tried to get a model from Blender 4.2 to Unity 2022 in USD. It omitted the main armature. I quadruple checked all settings^^
That Godot plugin you linked uses Blender to import USD files to convert them to glTF 2.0, which then will actually get imported in Godot.
Collada has been deprecated in Blender.
Yes, so much yes on the first part! Want to implement the simplest thing in UnityGLTF? You have to fork it, and force all your users to use your very special fork.
I assume you mean my 'nna' project with the second part? That serializes data into the node-names of the model's hierarchy. It is as stupid as it sounds, but it works reliably, and I don't need to modify any exporter/importer. The data is part of the file itself.
If you wanted to embed data into a format more legitimately, you would have to modify its exporter/importer, and the format would have to support extensions in the first place.