Why not just something like nim and that point, and straight up ditch 90% of the complexity?

I was answering to this other user:

> This is factually impossible.

> For anything larger than (very) small programs, Rust requires an upfront design stage, due to ownership, that it's not required when developing in GC'ed languages.

It seems that is not factually impossible.

Now, answering your question: It could be useful to use boxed types and later optimize it, so you get the benefits of rust (memory safety, zero cost abstractions) later, without getting the problems upfront when prototyping.