3) Instead of the subscriber pulling the slot info, why can't the publisher (via the walsender or a new bg worker maybe?) push the latest slot info? I'm not sure we want to add more functionality to the walsender, if yes, isn't it going to be much simpler?
Standby pulling the information or at least making a first attempt to connect to the primary is a better design as primary doesn't need to spend its cycles repeatedly connecting to an unreachable standby. In fact, primary wouldn't even need to know the followers, for example followers / log shipping standbys
