> I'd use PyPy which would've done wonders for responsiveness on the existing product and adopt containers for deployment.

That's an easy claim to make, but you don't know whether their stack would actually get much improvement out of PyPy. We've had trouble in the past using PyPy with C extensions. Trying to migrate to pure Python equivalents was a headache. Once we managed to get a PoC of a service running under PyPy, we saw very little improvement.