A little history that you can learn from. Original Business Case to the Board was for 6 wide-bodies for Jetstar and the reason Bruce Buchanan was sacked. He raised the point that he "can't make the model work" beyond that number. Revenue in the Qantas Group was plateaued for the last 8 years with 50% more aircraft and the reason Jetstar is reported as a Group and not in segments.
Currently a proposal is be examined to hand over some of the the B787-8s(maintenance free(paid for) for the first 4 years) so suggest the older ones. Revenue comes from full service so emphasis will likely be on that from now on. New destinations being examined and none are low-cost.
Don't think any or many will take up these opportunities but the question must be what happens in the narrow body domestic space in the coming years. Personal view is the Airbus 319/320/321 is the best fit just in what colour and maybe we will see direct entry B737 in the short term.