I recently booked 4 such tickets. The QF + 2 OW carriers thing is a good point, note that if you end up picking CX, you'll have to book that via the phone (i.e., spend the 2500 points per person booking fee).
I think there's also a transit rule in the OW Classic Award - while you can backtrack to the same city, there can only be one stopover, the others must be transits (i.e., <24 hours).