.”What happened to repairing the ceiling so that it cosmetically matches the original ceiling?” The owner is fixing a broken pipe, The thought of paying out a $1000 for the repair of the ceiling correctly might not have appealed to him. (You cannot patch a small section of the ceiling without leaving tell tail distortions, it has to be removed completely cornice and all, then new sheets fitted and a full paint job)
AS 3500, my plumbing code, says that I must have access to any trap or inspection opening in the ceiling space
For there to be drafts you need air to be able to flow in and out, for this to create a draft you already have at least one way out, so your fire rating is already screwed.
No IP address or email address was supplied so the we have no idea of where the person was from, I live in the sub tropics as do you, We build houses on stumps here to let the air move under us to cool it. We also build standard slab buildings with plenty of air flow and keeping the northerly aspect as window free as possible. Also the eaves are quite often vented to allow airflow.
Of course the other alternative, so as not to replace the whole ceiling at a large expense, is to install a fitted panel to keep it fire rated