Who says you need to feed it directly to the replica. Logical replication provides infrastructure for decoding changes, and you may fetch it any way you want /

Who says you need to feed it directly to the replica. Logical replication provides infrastructure for decoding changes, and you may fetch it any way you want / how often you want / feed it wherever you want (file, another database, ...). It would be trivial to write something that connects to a bunch of machines regularly, fetches the decoded increment and feed it somewhere (say, to a single database over a shared connection). See test_decoding / pg_recvlogical for examples.