Maybe if Elon Musk's Hyperloop between San Fran and LA works out, we could get something like that working here!
But seriously, high speed transport would be great. Very little of Australia's wealth comes from mining. It's a four or five percent from memory, and something like 70% comes from services. So the majority of Australia's wealth has come from opening up trade routes with Asia.
The vast majority of immigrants settle in our capital cities, which employ the vast majority of the people.
So things like well functioning infrastructure are so important to continue this wealth generating trend. High speed transport between the cities would have been an incredible boon to that, IMO.
That, and greater investment in innovation and entrepreneurs. Though our biomedical achievements have been fantastic, our IT / tech industry here is pretty much non existent.
The belief that our wealth has all come from digging stuff out of the ground and selling it, has been very crippling for our future, IMO. Mining companies make a small percentage of Australians wealthy via the stockmarket, but that is private business ownership, which is very different! They take the majority of their profits overseas, and Australian citizens see none of them.
If we had a burgeoning tech and startup scene, high speed rail links between the vast open spaces (or something similar), and other infrastructure advancements, then perhaps all that combined with our amazing natural climate and society, we would attract some of the smartest people in the world. Who otherwise end up in California, NY, London, Japan, the Netherlands, etc.
Nice beaches and friendly people can only get you so far, if the other aspects of life here don't compare on the world stage.