I am very concerned though about the dangers of totally dedicating the Oz airspace to a GPS only based air-nav system
it is not and would not be ONLY GPS based for Nav! nor is ADS-B sole surveillance around the Primary capitals that will retain PRIM and MSSR! ... are you deliberately trying to mislead?
.
... answer your own question
Bing/Dick
.
Is GPS 'the' nav system a nasty would use for guidance?
.
Even if it was, what would be risked by shuting down GPS at short/no notice?
.
In other words, how many industries, companies, government systems that rely on sole (or near to it GPS) use would be affected? ... would lots and lots of lives be put at risk? .... is that an acceptable risk?
.
Not to mention the number of critical systems that utilise the super accurate GPS clocks worldwide.
.
Or are you suggesting that even after an 'event' those exposures would be considered worth it to turn it off?
.
You tell us!!