mitmproxy is explicitly intended as an interactive MITM for debugging: "your swiss-army knife for debugging, testing, privacy measurements, and penetration testing".

What you're talking about here was never a goal. And being in Python means it's much easier to extend, which is also greatly useful.

Well, okay, got me. But you don't need to do what mitmproxy does in that case.

This isn't a replacement for a Bluecoat, this is a developer/debugger application.