What about compatibility with Python packages?

WebAssembly

I've unironically been looking for a decent way to run Python in the web, mostly for code sharing purposes (our app needs certain calculations in offline mode), so this could actually work for me.

Can RustPython be sandboxed properly when used as a scripting language? You can't do sandboxing with CPython. There is an abandoned sandboxing project for pypy, but then you'll be stuck with an old version of python.