Maybe something closer to migration management in mastodon? Two groups of moderators on separate servers agree to a common set of moderation guidelines, publish an event or setting which says “these communities are merging”, and from that point on they act like aliases for a merged community which share responsibility across servers.
These “merged” communities could be visually flagged as distinct from the normal rules / moderation of their respective servers to prevent conflicts arising from differences in server management.
Feature support would be limited by the server events are sourced from. E.g. if beehaw.org and lemmy.ml merged their technology communities, people on beehaw still wouldn’t be able to downvote posts or see downvotes, but lemmy.ml would unless they explicitly disable to feature as a part of the merge contract.
When subscribing, you might see a list of merged communities which share responsibility for moderating the final one, and you have the ability to choose which “entrypoint” you use.
My fave. Self-deprecating and fits the name well.