The logical thing to do would be to run one A380 SYD-DXB-LHR and the other MEL-SIN-LHR (or vice versa).
If you want to get from any capital city to London (barring ADL/DRW) then you can do it all the way on QF metal.
If you're in SYD and want to go somewhere else in Europe you jump on an EK jet in DXB.
Opens up countless more options and will increase loads on SIN-bound flights from MEL/BNE/PER and give people the option of the more popular stop-off in Singapore.
So logical in fact, that it'll never happen!
