Have you actually used this in a real codebase? Because it is the opposite of my experience in gradually adding types to a large python codebase. There's no extra complexity or slower development. It's not like you need to suddenly move to a different coding paradigm with FactoryBeanFactoryBeans... You just keep writing python like you did, but add types here and there to help clarify things and make your LSP (like ty) work better.

If anything, it speeds up development. Plus it helps give more confidence in the correctness of your code.