CASA aren't completely opaque - though their usual out applies (
Guidelines are not a statement about how CASA will proceed to make a decision in every case). Basically, if you meet the standard, looks like hearing assistance shouldn't be a problem. Or you can demonstrate that you can hear all that is required in an "operational test" (e.g. in flight).
see
ENT (ear, nose, and throat) - Hearing Impairment