You could presumably also look at a (oneworld) Global Explorer ticket rather than a oneworld Explorer. For a Global Explorer in business, the maximum mileage is 34,000 for $9,199 so that's somewhat cheaper than the DONE6 at $12,000. Without knowing your routing, it's hard to know whether that might work.
And speaking of creative options, perhaps your itinerary would be workable for a DONE4 with side trips to a couple of the destinations without actually buying the extra continents.