Bloggs. Traffic lights at each intersection ( or its equivalent ) would be un affordable .
Using the existing equipment and changing an airspace chart and enabling an alarm would be quite affordable .
Yeh, just change the airspace on the chart from G to E and provide a "Surely an enroute controller being able to do a bit of approach work at a place like Ballina can’t be rocket science. " will be quite affordable.
The class G controllers could easily issue an altitude alert... to the light aircraft that doesn't have EGPWS, because all the turboprops and jets have it and don't need the 1950s "lookout, you're heading for a hill". Benalla was horrific, but it was not an RPT flight and it was over a decade ago. How much are you prepared to stump up to pay for this service of yours? I don't see you whingeing about the hundreds of thousands of cars on the road that don't have ABS and which probably result in dozens of deaths every year. To replace them would cost millions, that's why.
You're like the Greens and renewable energy. Great ideas in theory, but SHOW US THE MONEY.