I think a good part of this is going to come in the form of custom Activity actions. I’m about to get into the underlying technicals of ActivityPub, so bear with me.
If you look under the hood, ActivityPub has a bunch of “Actions.” Like, Repeat, Note, and so on. They represent different things but they federate. Well, what if we made-up a bunch of new ones?
Example: chess. Actions for Start Game With So-In-So. Move one square to another, and so on. It wouldn’t just be generating text that the user sees, but it would be generating data that can be interpreted by a computer. The backend could evaluate if a move is legal or not, for example.
This plays into my fixation with rich presence this year, and why I got so pushy with the source code maintainers to not deprecate scrobbles. I think the future of fedi is in adding new things to it. If you look under the hood, you will quickly realize it can be so much more than federation of mere text and images.