Best option for me would be to merge the SL and NRL (as separate conferences), put together groups of four and build the season around that.
Australasian Conference:
West Sydney Group: Wests Tigers, Parramatta Eels, Penrith Panthers, Canterbury Bulldogs.
East Sydney Group: Cronulla Sharks, Manly Sea Eagles, South Sydney Rabbitohs, Sydney Roosters.
NSW Country Group: St George Illawarra Dragons, Canberra Raiders, Newcastle Knights, Central Coast Bears.
Queensland Group: Brisbane Broncos, Brisbane Brothers, North Queensland Cowboys, Gold Coast Titans.
Pacific Group: Melbourne Storm, West Coast Pirates, Auckland Warriors, Wellington Orcas.
European Conference:
West: St Helens, Warrington Wolves, Widnes Vikings, Wigan Warriors.
Central: Salford Red Devils, Huddersfield Giants, Bradford Bulls, Leeds Rhinos.
East: Wakefield Wildcats, Castleford Tigers, Hull FC, Hull KR.
France: Catalan Dragons, Toulouse Olympique, Aude Cathare, Avignon Bisons.
Play everyone in your conference once (Aus: 19 games; Euro: 15 games)
Play everyone in your group a second time (3 games)
Play one team from every group in the other conference (Aus: 4 games; Euro: 5 games)
Play one team from every group a second time (Euro only: 3 games)
Each team playing 26 games in the season.
Straight knockout play-offs (top of each group plus highest points from the remainder).
Conference final followed by World Club Final.
In time, expand conferences by adding extra groups in new areas. Easier to add groups of four from new areas than new leagues. They may get sides at times, but they will only pay a few cross group games a season.
A World NRL. That's the future.