I'm sure a fully staffed Radar site for all Airports in the World would indeed make it safer in some circumstances where CFIT is an issue. Yes Cairns is one.
For this example in YMLT during a missed approach in a high performance 737 it's my opinion that a fully staffed Radar facility wouldn't have made it any safer.....
And yes where I spend most of my flying ( VHHH ) HKG APP/DEP have indeed saved a few stupid operators from heading toward Lantau peak....
Doesn't it all come down to affordable safety?
Cost benefit analysis etc etc....