"We can't play more games because we currently don't play many games" isn't really a great excuse though is it
Agree mate - if the four nations doesn't return (which it looks like it probably won't) we plenty of room in the calendar for internationals, both one-off and series. We continue to have a mid-season rep window where England must play New Zealand alongside the Pacific Tests. Then post-season we must have annual Pacific, Euro and Atlantic Cups.
The big three then can play 6 tests post season: England can tour every second year and play Australia twice and NZ twice and the winner of the Pacific Cup then return to Europe to play the Euro Cup champions. During an English tour Aus & NZ will play England twice each, each other twice and both play the Pac cup champions.
Every other year the Kiwis and Kangaroos can play a warm up test against an island nation each, play each other twice then go north each play England twice each and then both play the Euro Cup champions. During these years England will play a warm up test against the previous years Euro Cup champions, Aus & NZ twice each and play the new reigning Euro Cup champs.
This gives the same benefits that the Four Nations gave but better; it gives access to the teir two nations to earn the right to play with the big boys hence giving the Euro and Pac cups more meaning (on top of the already significant meaning of a major trophy) but both Euro and Pac champions will get to do so pretty much annually, not every second year when the 4N gets played in their hemisphere.
7 tests a year for England and New Zealand
6 tests a year for Australia plus State of Origin
Minimum 3 tests a year for the best Pacific and Euro nations with the winners getting bonuses of between 1 and 3 matches with the big 3
If Australia choose to sit-out certain years, so be it, but the schedule rolls on without them and England and NZ play a 3 test series instead.