Where does it say that you have to get approval for an unpublished route?
AIP ENR 1.1-41 para 20.1, 20.4
Isn't a "published route" an issue if you're in a bug smasher...? You certainly aren't going to follow an RPT route.
In my head it seems to work like this and has always worked well for me given that much of the traffic comes from Sydney and Brisbane.
(Slightly out of alignment but you get the drift)