Support the usage of SOLID pods/ActivityPub
SOLID pods are kind of a container storing your private data and let websites link to it, if you allow it. It is a way to stay the owner of your data in a social web context. You can give people and apps permission to read or write to parts of your Solid POD. More on this you'll find in a short summary here.
I think it would be a nice approach to already use that for our federated and decentralized server-based multiplayer. So we say you can host the openage-part (your user-profile) of your pod with us, but surely you are always free to move anytime to another service and by definition SOLID pods support that easily (e.g. we just store the URI to the pod and include data from there).
That would also imply that under some circumstances it will be way easier for us to conform with (not just european) data protection laws, as we would include data from the pods instead of storing it on our devices.
Required server-side implementation
We could do that in addition to a mastodon's approach to decentralization as in @[email protected] could then forward to the pod or something.