Ah, okay. That is cool. It doesn't solve a problem I have (if I'm compiling to a target outside the browser, I'm going to compile to LLVM --> native, not wasm) but I respect why that's exciting.
You can write a program that has the capability to run isolated WASM modules written by others, without caring about the source language. Export some functions from your host program and you have a neat system for, say, user-written extensions.