Something that appeals to me about the multitenant security story in WebAssembly is how easy it is to provide alternative implementations for system calls. In most wasm implementations, you begin with a "raw" wasm runtime, and explicitly provide host functions ("system calls") that the wasm code can call. Nowadays the wasm implementation is likely to provide a wasi implementation out of the box, but it's simple to replace the implementation of one or more of the wasi system calls with your own (or define your own syscall interface entirely!). In this way, you can put in extra protections, monitoring, alternative implementations, etc where you see fit.

It's kind of like a built-in mechanism to adopt gVisor's approach to container security. Implementing gVisor is a gargantuan task that few companies would embark on; comparatively, doing the same in wasm is absolutely trivial.