Yeah, I'm very intrigued by unikernels myself; as far as I know, I'm the first person to have gotten an Iron web app running on Rumprun. I figured I'm the first because I had to send patches to make it work :)
I guess my point is that even if vague designs are relatively a monoculture, that still means that anything that fits inside that box is going to be reasonable to port over. And I'm glad that it's so easy to not use the standard library for other cases; my little kernel doesn't yet have processes or files, and Rust works for it just fine. Well, it doesn't have them yet, anyway... hopefully soon.