The Warriors already fit the all of NZ niche, and they'll have been doing it for 30 years by the time the next club comes in.nz certainly won’t be based in one city either. It will obviously be Christchurch based but then Wellington Hamilton and Dunedin should get games. Other than Wellington they all have great rectangular grounds
they will basically be a non Auckland nz side
Splitting games between cities like that would just put the new club in the position of trying to fight the Warriors for the tile of 'the NZ side', when odds are that's a fight they will lose (unless they are winning premierships, but you can't bank on that type of success) because there are no major incentives for most of the Warriors fanbase outside of Auckland, and the home city of the new club, to switch teams from the Warriors other than the new side is different.
So all they'd achieve by going down that route is confusing their image by trying to be everything to everyone, and putting themselves into a direct conflict that they'll almost certainly lose. It's also just generally a bad idea to attempt to cannibalise a club's fanbase like that.
So instead they should pick a market then be extremely parochial within said market, i.e. the worlds against us beleaguered underdog fighting the behemoth style image. Or in other words a pre-2005 ACT Brumbies style image.
I'm not necessarily saying that they shouldn't play games outside of their chosen market (nor the Warriors outside of Auckland for that matter), but where they are from and whom and what they represent should be crystal clear, otherwise they'll just come off as a plastic corporate creation that doesn't really represent anything, and only exists purely for corporate business interests, i.e. GWS... In a small market like NZ that'll be enough to cripple the club.
If the NRL wants market coverage in NZ then it's going to need at least 3-5 teams in NZ anyway. So given time the other major cities/regions will get their own teams, they just have to be patient.