In theory and not super big scale you can already architect instances layout in a way when every reactive collection is in separate database, put meteor instance above it and provide DDP method which will feed you information based on variable query.
Than in another server instance you can DDP.connect, create collection, subscribe and than query it as you want.
I would expect if you connect like it in server startup, in server method you can just return cursor above that given collection which represent cursor above remote collection.
Still it would probably lag few seconds so not true realtime expirience.
But for scaling user facing instances it seems like something I would try if I need it
So I dont feel there is some special separate package needed - just strip collections to separate databases, put meteor instances above them.
And in your standard meteor instances replace local collections with remote ddp connect + collection + subscribe.
Sounds easy in theory, any1 tried it, what was the issue?
And I am going back to learning neo4j, cause I love relations