pip can be configured to use a local warehouse, and there are warehouses that transparently proxy to pypi, but caches any previously fetched result. E.G: https://pypi.org/project/proxypypi/

Since you control it, and it's read only from the outside, you can actually expose it even outside of your network.

But indeed, it must be replicated for npm, cargo, maven, docker...

There is a startup idea here :)