Strings Rewrite
Created by: ddworken
No idea if you are interested, but when I was first getting started with Rust I wrote my own implementation of strings in rust. It already has support for Unicode, multiple threads, and a number of other helpful options (along with all of the other options that strings offers by default).
If you are interested I would be more than happy to re-license it as MIT so it can be merged.
I'll admit the code quality isn't great (if we're merging it I'll spend some time cleaning it up!) but it will save you some work with adding all the extra features.