However, what you are doing is not supported for a reason. You aren't
supposed to be changing the dataset the slave is supposed to replicate
like that without forcing a reload of the DB (which is what -c is going
to essentially do).
True, but it would be handy :-)
I am thinking of the case where the slave server is in a more exposed
position than the master (maybe outside a firewall). In such a case it
would be silly to trust the slave to only take what it is 'supposed'
to have, so the replication subset has to be defined by ACLs on the
master.