There is a fairly active effort to come up with a safe transmute API, see #project-safe-transmute
There is also a pre-RFC here and someone is drafting an RFC.
This would be nice to see - right now we have 5 incompatible crates for the job, each with its own downsides
In fact this is big enough to warrant its own repo: https://github.com/rust-lang/project-safe-transmute
typic crate is pushing the envelope on what kind of transmutes are possible in safe Rust: https://www.reddit.com/r/rust/comments/eh67wi/typic_safe_zerocost_transmutations/