@robin @volkris Now I'm even more confused. Like I said, the devil is in the details, and it might be impossible to justify the 'over' preposition in any direction without showing a little bit more about what you expect to be sent over the wire...
The proposal is an interesting idea, but I think if you write down what's sent over the wire, it'll be clear that either 1) it's not ActivityPub at all (so it's not AP over ATP) and/or 2) it is AP aka HTTP (over ?), but the ATP is superfluous