I like this idea as well, if it would do a different kind of work at a different community level. The thing that's missing here is that it recenters control at the mod level, rather than at the user level - and I can see how that might be more appropriate, if I'm also enamored with the idea that individual users would gain access to a new kind of influence (should they get popular enough with their community sorting).
Sure (and hi!)
The first part of an idea is just the aggregation of communities into a meta-community, like Reddit used to have meta-reddits that users could build, taking multiple subreddits and joining them together into a single feed. Here instead, we would be joining together multiple community instances - for example, say, !android@lemmy.world and !android@lemdro.id, both instances of "android" communities with different users and different feeds. I want to be able to join these two "android" communities into one feed and interact with them as if they were the same "community".
The second part of the idea is that users could create these meta-communities (lists of communities) and share invites or links to them, similar to Spotify playlists. Subscribing users could then choose to "update" their meta-community along with all of the other users following that meta-community to match the list of the originating user.
The third part is that the system would check to see if the subscribing user (or creator of the meta-community) could actually interact with all of the instanced communities from the one they are currently at, and let them know if there were issues with federation.