Here's how I think a second NZ side could work in NZ. I'm not saying this is what SHOULD happen or that it would be a huge success, (I'm staying neutral on that, but I'm at least trying to provide a model that is practically feasible.
Assuming a season of 25 full rounds in an 18 team comp, with two pools of 9 teams (Sydney and non-Sydney), with each team playing the teams in their pool twice and the teams in the other pool once, you'd get either 12 or 13 home games per season.
NZ2 to be based in either Wellington or Christchurch. Based out of the existing stadiums or the new Christchurch stadium once its built.
A commitment to play 8-9 at the home base per season and 4 at the second city.
assuming at least 1/3 of home games are Sunday afternoon games (midday AEST timeslot) that would keep the potential number of night games in Wellington down to the required 4 if it were the home ground.
Season ticket options could be split into 5 tiers- All home matches, an 8-9 ticket option for the main home ground, a 4 ticket option for the second city, a 1-2 game package for fans in Aus and a non-ticketed membership.
This doesn't of course address the issues of funding and improving NZ junior pathways. But its a model that would allow the use of the best existing venues and capture support from the widest possible area of the country without making travel too onerous.