I might be missing what you are trying to do but can't you get that optimization today with using FFI to use native modules in your server side code?
The main benefit would be shipping a single WebAssembly module to target client and server (e.g. the same benefit of sharing JS between the browser and Node).
You can't run it on an arbitrary OS or ISA without explicitly creating a build for that specific ISA or OS.
You can now simply do
node --expose-wasm
> buffer=fs.readFileSync('test.wasm')
> WebAssembly.compile(buffer)
FWIW you can already use AOT compiled code in Node.js (native modules). Will WASM provide more benefits over that?
Portability for the AOT compiled modules?
I haven't seen any official solution for AOT from NodeJS foundation. Having "Official" WASM support drives/drags the community in a standard direction.