RFC text: https://github.com/jswrenn/rfcs/blob/safer-transmute/text/00...
I don't know what the status quo is, but it is very exciting work.
There are also crates in this domain that work today. The two I'm aware of are https://docs.rs/zerocopy/latest/zerocopy/ and https://docs.rs/bytemuck/latest/bytemuck/