Personally, seems like too much effort for something that would still need to (and fail to) have some sort of a link between the two, so I could go from the planning over to implementation and back easily. In reality, that'd get lost in the noise of dozens of sessions - I mostly just want the harness to help me do work and otherwise get out of my way, not make me dance around it. Ergo, the more context management it handles, the better!
It's part of why I really dislike to work in Claude Code, and found it too unwieldy. There I have to keep dancing around it to manage the context in a sensible way.
I mean, not in Pi at least. In Claude Code it is a chore.