Cross posting my response just to let you know of the eventual outcome. Thanks very much all for the advice.
Going: J redemption via Velocity points converted to Krisflyer on SQ: SYD-SIN-ZUR $475 in YQ/taxes.
Returning: Positioning flight to DOH - Y class QR: MUC-DOH - QFF Points
AAdvantage J redemption on CX: DOH-HKG-BNE = $1285 (45,000 miles + taxes)
So a total of $1935p.p Return Australia to Europe in Business on SQ and CX (with a small 5 hr Y flight on QR).
I could have got this down even lower to about $1550 by using my Velocity points to go from BNE-IST on EY for only 110,000 Velocity and $85 taxes.
There were other AAdvantage options for the return leg such as QR/QF: DOH-PER-BNE or QF: DXB-MEL or EY: AUH - BNE.
- the sweet spot for these AAdvantage redemptions is the Middle East/India to Australia zone which is 45000 points for J. Note you are allowed to go via SE Asian hub (SIN,HKG,BKK etc)