I guess it might work. (737 on SIN-BOM)
The current 737 flight comes in from Perth in the evening, so if the departure ex SIN times in with transit pax from SYD/MEL/BNE, then filling it shouldn't be too hard. Then do the same in reverse. Not sure what the yields would be like though.
QF currently codeshare with Jet Airways on the route and they use a 738, so what's the difference? Surely the QF product is an improvement on that!