there's a few others options (though appreciate not all realistic).

Gold Priority Reward - means if you are willing to spend double the Avios and book at least 30 days out, they'll open up space (believe A class needs to be available though). (not overly realistic you wanting to blow 800k but it's generally an option and a very good one on e.g. RFS').

Jokers - a GLL benefit that frees up space (provided certain criteria / rules are met).

as others have said, flight do become available - also with partners - though you may need to be flexible. I've been looking at SYD and e.g. MUC - SYD has seats on QR (J to DOH and F to SYD). not avios cheap but if you are flexible on starting point, dates and to some extent, routes, there's ways of getting in style to OZ).