When it comes to the final of the NZ provincial premiership, the final is more often than not Auckland v Canterbury. So there is some league talent in the South Island, and some league interest in the South Island as well, This is shown by the fact the Roosters v Warriors game in Christchurch attracted a crowd of over 20,000 even despite dodgy weather on the day.
So a North Island v South Island "State of Origin" concept is not a bad idea. Up and coming talent in NZ does not get any recognition - in terms of the national provincial competition it is only the Grand Final that gets televised. The Auckland competition, the Fox Memorial Shield, does get limited TV coverage but viewer numbers are not very high because it is only an Auckland thing.
It would be good to get some of the up and coming talent some exposure. It would provide some scouting opportunities for NRL clubs, and don't all league players in Australasia aspire for an NRL contract? Maybe it could be squeezed in before the Toyota Cup game as a curtainraiser to Warriors games - a tripleheader. However thar would give the Nth Is an advantage because they would get more home games than their southern counterparts.
Most of the players are from Auckland but in recent years Canterbury have had their fair share of success in the finals against Auckland so it would be an even enough competition, and there is only one way of finding out if it works - try it!
One idea that might be worth looking into also that I've just thought of: a triseries between an NZ Provincial Championship XIII, a Qld Cup XIII and a NSW Cup XIII. It can be staged after the club season is over, possibly as curtainraisers to Four Nations games when staged downunder and as standalone fixtures when the international stuff is in that other country. Maybe even bring in a fourth team, possibly a PNG side, so it can be played with a doubleheader for three consecutive weekends and then a GF.Maybe have the final in NSW, with NZ getting a double-header, Qld get a double-header and PNG get a double-header if the internationals are overseas. If the Quadnations is in Australasia, then each Quadnations match can have a match from my proposed Quadseries as a curtainraiser. Simple!