This sounds suspiciously like the composable ostree filesystems used in Flatpak. In fact, this could be a way of providing the Rust shared lib environment exactly up to the compiler version that the application was built with, as required by the application's manifest. Different versions of Rust shared libs can be installed side by side as needed for the applications. The rest of the world is not there yet, I think; maybe Microsoft's SxS, the most underappreciated Windows feature out there, could be similarly utilized?