I think it might be fun to make a mutex library where you must give every mutex a u32 priority, and you are only allowed to acquire mutexes of strictly higher priority than any your thread currently holds, with crashes if you violate this rule. This completely prevents deadlocks.

The Cloudflare outage was caused by an unwrap(). I think Rust's standard library is very well-designed overall, but I think unwrap was a mistake. Code that can panic should stand out—e.g. with panic!()—and "like panic! but harder to spot and easier to reach for" is a bad pitch.