But then what's the point, what do you do with it that the compositor can't?

Then instead have stable window IDs so the compositor can do its job properly - there is absolutely no need to self-position and outside of certain privileged apps I absolutely don't want random programs to move their windows around.

Stable window IDs? Are you gonna use the document path and the panel number or something?

I wasn't aware of this proposal, but I pretty much nailed it and though of the same thing: https://news.ycombinator.com/item?id=49836487