Nobody really self-identifies as Austronesian though, it’s a term used in Anthropology but not something willed themselves identify as in everyday life. On the other hand Polynesians readily self-identify as poly and recognise other Polynesian people as such (even if they often have bitter rivalries in the case of Samoans and Tongans)Surely there would be more capital in Wellington than Christchurch?
An Austronesian themed club would appeal to Austronesians living all around the world -- there are 386 million of them -- but very few would become active supporters.
If it's just a South Pacific islander themed side then that nber dwindles significantly. There are just 2.5 million Polynesians.
There are 11.5 million Melanesians.
Melanesia Population: current, historical, and projected population, growth rate, immigration, median age, total fertility rate (TFR), population density, urbanization, urban population, country's share of world population, and global rank. Data tables, maps, charts, and live population clockwww.worldometers.info
We already have Melanesian teams in the Queensland Cup and NSW Cup providing a valuable pathway for rugby league players from PNG and Fiji.
I don't think a racially exclusive team at the professional level can work a there's just not enough people to make provide the money that it'll need to succeed. There's just 880k Polynesians in New Zealand.