Nemisis
the BCA is a constantly evolving document. Many design features of the past now do not meet current BCA rules.
However the building codes administered by the local council do not compel any owner of property to upgrade to meet current standards ( can you imagine the flurry of building work that would arise every time a new BCA was published).
So the OC is not required to upgrade balastrades built to old standards.
However if the balastrades have fallen into disrepair, the OC must repair them. Depending on the extent of repairs required, the council may require that the balastrades be upgraded to the current standard.
If the state of repair is not the issue and you just think they are [not] safe, consult other owners and see if they are the same opinion. Write a letter to the secretary asking to put a motion to the EGM to renew the balastrades.
If enough owners agree with you it would pass.