The absolute requirement is that these must be binaries that could go into /usr/bin one day. No python, ruby or js stuff. Not that dynamic languages are bad/evil, but I think system utilities should be binaries. I also think it's interesting that people are writing replacements in Go/Rust/Other that rethink some unix legacy. Replacement doesn't mean better in all cases. I just think it's an interesting time but also a good measure of what these compiled languages can handle/tackle/address. Will we see larger and more impressive CLIs? Or will the feature sets be about the same but the quality/stability/safety be better?
It's going to be reductive to explain some of these tools in one line.