Regarding Rust's compilation slowness, wouldn't a Rust interpreter be a good solution for developing code? A Rust interpreter would drastically cut down slow compilation times, and then when the final product is needed, the Rust compiler would kick in.
It's not clear that it would, or that the execution time of said interpreter would be fast enough to make it work. Miri interprets Rust code and it is, from what I hear, orders of magnitude slower. And for some applications, even debug builds of Rust are too slow. So it really just depends.
(It is also going to be slower than an interpreter focused on runtime speed would be, the point is more that interpreters aren't magic.)
