I am currently working with Flutter and Dart,
Having the same level of memory safety that Rust has can be accomplished in one of two ways: garbage collection, with the associated cost, or extra annotations and robust type system. Changing any existing language to do that would diverge enough from the root language that it would no longer be the same language, losing the benefits of using an existing language to begin with, and foregoing the benefits of building a language that accounts for the way it manages memory in its features.
I also personally believe that it'll be easier to make Rust easier to use than to make GC languages faster or non-memory safe languages safer.
Checked C is another.