Some ideas for NZ-based expansion clubs...
I think a 2nd NZ club from the South Island (Based in Christchurch, some games in Dunedin, Nelson or Invercargill) could be called the Keas - named after the alpine parrot. In provincial league here, the Canterbury (Christchurch) team has been named the Bulls, but I think something different would encompass the whole south better.
Wellington-based team would probably be the Orcas.
Another possibility is a Waikato/Bay of Plenty club (most games in Hamilton, some in Rotorua).. not sure that a good name would be - teams from that region have used the names Cougars & Stallions in the national championship in the past, but those are a bit rubbish for NRL. Given that dairy farming is big in the Waikato, I'd say the Bulls name would go well there.