You could split it to four regions, and play two-legged semi final stage, one game played in each region, and a final. Maybe a third place playoff so each team gets three games. I'm not sure what the regions would be like

, just for the sake of conversation:
Hull XIII (Hull FC & Rovers)
Yorkshire (Cas, Wakey, Leeds, Hudds, Bradford)
Lancashire (Wigan, Saints, Wire, Salford)
Expansion XIII (Quins, Crusaders

, Catalans)