I don't know if ActivityPub, XMPP etc could handle it or if new protocols must be invented, but just think about it:
Some sort of independent consortium could get together and decide on some rules for a game.
"there are some enemies (ID E0001) who has this ammount of HP and deals this ammount of damage from this distance"
"there are some weapons (ID W738201) that deals this amount of damage over this distance and can sustain this amount of wear and tear"
Just as an example
Want to play a game of Good vs Evil on a distant planet, with high tech weapons and realistic graphics?
Sure, pick this client!
Want to play a game of orcs vs elves in a forested fantasy world with magic and early GTA style graphics?
Sure, use this client!
You all still play together! You just see different things.
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