It wouldn't be a complete decomposition, of course, a person watching would see your thinking unfold. I think speculative decomposition would be very interesting, especially in retrospective if we could see the rabbit holes we went down.
Decomposing is easy since we naturally have to do that as we work. Heck, those 500 tasks are probably in your shell, browser and commit histories, mixed in with a bunch of other junk.
The problem is tools like Jira make this heavy-weight, doing it up front makes it nigh impossible, and having others review all this stuff and it becoming promises blows up the LOE significantly. And, I don't think I'd want to be under that much of a microscope as I work.
But if it were very lightweight, where I'm just posting my thoughts and can see them as a quick dependency diagram, and maybe attach notes, commits and URLs to them, and other people can see them, that'd be pretty helpful.