An approach like that would be at constant war with the borrow checker in Rust. Apparently it is possible but there is enough friction that these guys went a different route.

I would also have instinctively reached for a large VM reservation to exploit demand paging. I have used that pattern a lot in C++ but not in Rust, so I don't know how difficult it would be to implement there.

Rust supports punning via pointer casting, but you'll want to use #[repr(C)] on any data types used