You can transpile this demo to C++ with IL2CPP. It's built into Unity for iOS/Android platforms, never tried to do it on desktop, but I think it must be possible.
Compiling Linux to WASM (yes I know it has been done for single-threaded Javascript, but it would be interesting to know how this would perform on WASM, with threads).
And compiling VirtualBox to WASM would also be cool. If only as a performance indicator.
Also interesting would be to run other virtual machines (JVM) inside WASM, and see what the performance is.
Also interesting: compiling Firefox into WASM, and running it on Chrome (or the other way around) :)
Further, I'd like to see a good test of multithreaded/shared memory performance.