I've been thinking about this a lot as I consider the scripting language for finl.¹ I had considered an embedded python, but ended up deciding it was too much of a security risk, since, without writing my own python interpreter (something I don't want to do), sandboxing seems to be impossible. Deno is a real possibility or else forking Boa which is a pure Rust implementation of JS.

1. One thing I absolutely do not want to do is replicate the unholy mess that's the TeX macro system. There will be simple macro definitions possible, but I don't plan on making them Turing complete or having the complex expansion rules of TeX.