I think we could strike a balance. Don't put this stuff in the standard library, but have a category for crates that are officially blessed (or even maintained

I think we could strike a balance. Don't put this stuff in the standard library, but have a category for crates that are officially blessed (or even maintained by) the core team, such that if you trust the Rust stdlib then you should be comfortable trusting these crates. Then provide binary distributions for the built crates for all tier 1 platforms at least (ideally for any platform where a binary distribution of the stdlib is available) and teach cargo how to download those. This way we maintain the ability to version these crates and have breaking changes, but without the overhead of having to recompile these crates.