Your question is Order Flow Without Changing Core. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Given an existing order flow system of manual actions where a customer makes an order, it is processed, it is billed, and it is shipped, with each step requiring a team member to upload a file to a shared filesystem and send it to the next stage, design a supporting order flow system without making changes to the existing system.