EA has no need to be able to extract data from the game (music, sounds, w3x files, whatever else) since they have the source files available. So they have no use whatsoever for an extraction tool. So they aren't going to devote programmer time to writing one.
worldbuilder.manifest is not necessary, and can be extracted from the files if needed. There is nothing that having worldbuilder.manifest will change your ability to do.
You are incorrect.
wb.manifest is required for most civilian structures art to work and all the stuff that's in the static.m or global.m.
i.e. GBOrbit* are defined in this file. No file --> no art.
And it's extraction is futile if the SDK does not read and use the file.
No, you are wrong. Even with it, the art will not resolve properly, and you will still not be able to get civilian assets to work. It has been tested, and confirmed to not work. It's just down to how the build process and game loading work.