The whole model of having an OOL/CNS-NRT service is to allow as many connections from Melbourne, Canberra, Sydney, Adelaide ect into these northern ports to allow for a fuller B788 to continue its journey. Its more time efficient than say back tracking from Sydney to Melbourne to Tokyo. ZipAir, lacking any onward connections would crumble on CNS/OOL routes very quickly, as barely if any of the current JQ services from CNS/OOL had locals on board (part of the reason why JQ moved OOL to BNE, to attract more locals). ZipAir thus could only sustain themselves in Sydney which is already competitive with at maximum, 5 daily services. Or Melbourne which has 2 at most.
ZipAir is wholly owned by Japan Airlines which is making grounds in terms of market share in both Melbourne (which has been consistently had an extremely high all year load factor of 90%+) and as of recent, a B77W service into Sydney. I dont think they would want to split up potential seat bookings across more flights which at the end of the day reflects onto JL's Financial Reports at the end of the FY.
A 9 abreast config in a 787 is 17.2" of width. The width of the "Best" economy class products (10 abreast of Qatar and Emirates B77W) is 17" and the A321neo XLR's seat width in Economy is 18", in that regard I'd rather take the A321.
I havent seen people complaining about Air Canadas, British Airways, United, American Airlines or Air Frances seat pitch of 31" on long flights. In fact, Air Canadas Y product is the exact same as Jetstars Y in Economy on their 787 products.