I don't like seeing this idea raising its head again, but it was expected with the change of government. Especially with them looking for new ways to raise money.

It's sad that even a 10% tax on private imports would still be cheaper than bying stock that came here through corporate importers (who charge the "Australia Tax").
So instead of supporting consumers who are just competing against the companies that are making excessive profits by over-pricing the items they are importing, the consumers are being forced to pay more so that these businesses can keep charging their "Australia Tax" on items... leaving consumers having to pay more with either option.
Businesses already succeeded in having duties scrapped on most things in the last 20 years, especially with several free-trade-agreements now in effect... but they didn't pass on the savings.
Consumers still import privately because it is still cheaper. So now the Businesses are demanding "personal/consumer" Duty tax (the proposed GST) to force more people to buy their inflated priced items. As noted by GP and others, it won't work unless the tax/Duty matches the profit margin imposed by Businesses on items here. So even if the 10% is instigated, Businesses will still demand a higher tax on private importers (Consumers) to force people to buy their over-priced products, and maintain their own excessive profit margins.

Capitalism before Competition may well be the priority of individuals and businesses - but the reverse should be the priority of the politicians/government, to keep it in balance.

Now that the Liberals are in power, who are funded by Business and Retailer associations, expect more (direct and indirect) expense on the consumers, as that's the ideology of their "Right Wing" fundamentalism - "survival of the fittest".
They won't care how much extra it will cost the rest of us who are struggling, as long as they get their share of the money in the end (the implementation & enforcement of a $30-minimum import GST is said to be about 65 cents in every dollar raised, and if the Government wants that full dollar, you can bet that the extra 65 cents will be a cost passed onto consumers somewhere else).

One thing I don't like about these contemporary capitalist politicians - they are oblivious of what the rest of us have to endure because they get everything paid for WHILE being paid a wage... and if they feel they don't have enough money, they get a pay-rise. Plus, they get their pockets lined and retirements covered by minority interest groups, who don't have the interests of the majority in mind (that a democracy is supposed to be focused on).
(and it's both major parties that have interest groups or wealthy friends in their wallets... and our "saviour" the United party is run by a Billionaire - who probably doesn't even know what tough, week-to-week, survival budgeting even means.... and he used to BE one of those minority interest groups funding and steering the Liberal Party)

People who have the determination to change the system, don't have the money or power to go up against the system... and people who do have the money and power aren't interested in changing the system, only profiting off it like the existing politicians.