Although I am probably not alone in believeing that QFi has a limited future, as its high cost structures in which everyone from management and A380 pilots down are overpaid in comparison with the vast majority of other airlines make it very difficult to see it ever again being profitable, a similar timetable change to what Himeno and Flyerqf discuss above would increase patronage, all other things such as competitors' fares being equal.
0510 - the current QF9 timetable - is not an attractive time to arrive at LHR for most, especially leisure travellers who purchase the majority of seats (albeit at less revenue per seat for QF than its business patrons).
An evening arrival in MEL is attractive as it means most of us can go to bed at a suitable hour soon after we arrive at our homes or hotels, while a 1330 or so arrival time at LHR means travellers are at their hotels at 1530 onwards which means an easy checkin - no dumping of luggage at 0800 with a 'Sir, come back at 1400' from the hotel receptionists.