How do you achieve a government that is both big and efficient?

Without the government.

Politicians should get wings clipped on infrastructure

I think this idea has merit. An independent fiscal authority to complement the Reserve Bank - Infrastructure Australia if you will, but with teeth. This will improve the quality of chosen infrastructure projects, basing them on economic value, not political convenience. It could also encourage fiscal stimulus during a downturn when monetary policy approaches its limits. Not only is this something over which monetary authorities have been pleading with government since the GFC, but by helping monetary policy normalise faster, it can also help avoid unintended consequences such as housing and stock market bubbles.

But this is still a democracy, after all. So to keep these independent bodies accountable to the public, elected officials can still determine the bodies' objectives. In the case of the RBA, the government determined in the Reserve Bank Act 1959 that their 'charter' should be to maintain a stable currency, full employment, and the economic prosperity and welfare of the people of Australia. The Act also requires them to maintain the stability - and manage the risks - of the financial system. But achieving those objectives must be within the scope, power and authority of the body itself, with minimal interference from government, in order to maintain their credibility.

Many people want the government to do more for society, but don't trust it to do it properly. Well this is one way to achieve big government - without the government.