I like the 75% steering committee vote. I think you want to keep it to a minimum. Charter absolutely makes sense, and CoC makes sense simply because changes to a CoC can rip a community apart.

I think antitrust and trademark don't need the 75%. Really what they want for changes is "Don't change these unless you know what you're doing", and the same is true for the project's license, notice file, dependency-decisions (based on licensing) etc. Community norms will protect those two files from being unreasonably modified.