People have had a hard time learning Rust. I also get gripes about its inconsistency in language syntax. The FFI I hear is good. It certainly doesn't output to SPARK or a C subset designed for easy, static analysis.
So, Rust ain't the Ada makeover Im thinking about. It's also in a stability-oriented freeze of existing design right now. So, the makeover will need to be a different language.
I won't lie to you. It took me longer to produce good code in Rust than almost any other language I've recently learned. But it's worth it; it's quite simply amazing that it is capable of guaranteeing what it does, with nearly zero overhead. Also, I'd say in many ways it's simpler than C, because it has no undefined behavior; I don't need to concern myself with any of the nuances that I had to learn in C. I highly encourage you to give it two weeks, that's what it took me to become hooked.
That type system is pretty sophisticated. You could probably slap a FP front-end ala Haskell but that would hardly make it more accessible. Might as well just bite the bullet and learn the language.
So, Rust ain't the Ada makeover Im thinking about. It's also in a stability-oriented freeze of existing design right now. So, the makeover will need to be a different language.