Your strata committee needs to talk to an experienced strata lawyer right now. You also need to put an item on the agenda for your AGM along the lines that “The owner of lot XXX be required to remove the unapproved changes to common property resulting from their renovations and restore common property to its previous state OR seek a by-law ensuring ongoing maintanance of the changes, as dictated by Section 108 of the Strata Schemes Management Act 2015.”
A second motion might read: That the strata committee inform the local council about unapproved changes to common property attached to lot XXX to establish whether they are in breach of building codes and development approvals.”
Now, that wording is just mine of the top of my head and a strata lawyer (not just an ordinary solicitor) will come up with something more pointed and effective,. The main this is you need to get these items on your agenda right now.
Once they are there, the will come up in a strata search and you will save youreselves a world of pain when a new owner fights to have these clearly illegal changes approved or removed (possibly under council orders) at the OC’s expense.