Good point, it is well known that speed of machine code varies greatly depending on what language was used to generate it. Jokes aside, I really don't see a point in this. The safety guarantees of Rust are thrown out of the window the second you call dynamically generated code.

Clearly that isn't the case, surely Mike Pall would have heard of it, when he brought back LuaJIT from the future, that is.

Not without being a JIT. See Cranelift. I've used it to make a Befunge JIT in Rust