Obviously Rust has some features, like async, that are not needed for 'C with safety'.

But in my experience you need most of the other features. So any 'C with safety' will have a lot of the complexity of Rust. Though of course the syntax and defaults may be different.

At some point it becomes very subjective. Does a language need a UTF-8 string type, or is an array of 8-bit characters enough?

The research question would be, what is a minimal subset of Rust that still allows for programs that are commonly written in C to be easily written in this subset.

Some things, like the tuple type, or 'if let' can be removed, but is it still convenient to write programs without them? Closures are a bit tricky to see if they can be removed.

In any case, C struck a very good balance between being small and powerful. In my opinion Rust strikes a similar balance. Rust is a lot bigger, but it gives powerful tools to write reliable code.