Warriors wouldnt need to completely revert to Auckland, but define their catchment as Auckland, Northland, Waikato and the Bay of Plenty, and encourage them to move a game or two each seasons to Hamilton and Rotorua - both within 2.5 hrs drive of Auckland, and home to another half million or so people all up in those regions.
There's something of a natural divide through the central north island anyway, of places that tend to look towards Auckland as "the city" or towards wellington, and that'd fit that conveniently.