I would not worry about spending money to get gold with QF ; I would suggest looking towards status with AA

You dont need to travel in the US. By flying BA from SYD-LHR one way in business class and taking the platinum challenge that AA offers ( costs USD250), you can get around 48,000 AA miles plus platinum status ( same level as QF gold ). If your BA trip is anytime from 16th June, then you will have platinum AA status through to end of Feb 2016

The type of travel you do seems feasible to maintain AA status

Looking at the redemptions with AA, 60,000 points is enough for 1 way business class Australia-Europe ( 1st is 80,000 ) with no surcharges unless travel is on BA. Compare that with the 128k and the 192k PLUS surcharges that Qantas charges and I think you will be well ahead

You could purchase the remaining miles needed to get 60k for less than Qantas's surcharges

You can earn miles to AA flying on Qantas ( even if it is a codeshare on Emirates )

I think that using USD250 to get AA Platinum status when you do a BA trip to Europe will be of much better value than paying for a trip on QF