Wrote this in another thread but an 8 nations makes sense to include England, Fiji, PNG and France. 5 week tournament, two pools of four nations a semi and a final. 8N would have a point of difference to the World Cup because you have guaranteed group stage blockbusters that you can schedule. Could be a real crowd puller and money spinner in both NZ and Australia plus would give Pacific nations a chance to host some matches.
Lock it in once every four years between world cups so we have a major tournament every two years.