I wasn't suggesting any proprietary APIs or libraries - only that we get to use the /language/ of our choice.

Also I'm not talking about 'functionality [...] from other technology stacks' - I'm talking about getting to choose the programming language.

To current client code, everything would function exactly as before. It's just that you would be able to write new code in any language that can compile to the bytecode the VM understands.

The set of languages available through Emscripten doesn't compile most popular languages. If it did, it would likely fulfil what I'm hoping for, but I'd still be interested in whether it's the best option to compile to a subset of JS in order to run on a VM designed for JS.