One of the control motivations here is that rustc and cargo have _explicit_ interface stability guarantees. Imagine a vendor shipping rustc and cargo + 20 subc

One of the control motivations here is that rustc and cargo have _explicit_ interface stability guarantees. Imagine a vendor shipping rustc and cargo + 20 subcommands that are not behind the -Z flag. People may start relying on them and be annoyed of the Rust project if that happens. For that reason, you need explicit permission here, because we want to discuss with you how to phrase the messaging to avoid these situations.