Jetstar could base the 787s in Singapore and have a lower cost base compared to Australia. Using SIN as a hub certainly works for SQ. Daily services from the Australian capital cities into SIN then onward to Europe, China, India, SE Asia.
Sydney - Bombay may not be viable but a feed from SYD, MEL, PER, BNE, ADL into SIN and then onwards might be, especially with the cost savings.
Leave the high yield LHR route to mainline and open up new routes which previously wouldn't have paid.
Get back at SQ for starting Tiger Australia as well.