I think the NH sides really need to assess their tournaments and how they prepare for the world cup. There seems to be too much reliance (frankly sentimental affection) for the 6 nations, which is (lets face it) a second division tournament with a tired format that doesn't really seem to help prepare teams for the world cup.
And the nonsense that is the British lions should be consigned to the dustbin of history. If you are effectively accepting that you need to put together the best players from four national teams to have any chance of beating the big three SH sides, then you have badly lost the plot.
I think that there may be a rather deeper issue, PD. For years, the International Rugby Board, now World Rugby, was dominated by Europeans. In the 90s, that domination moved to the Southern Hemisphere, and it only fairly recently that there has been a more level board make-up. Of the exec. committee, 4 are from the Southern Hemisphere (2 from Australia, and 1 each from NZ and Africa), 3 from Europe, including the chairman, 1 from Japan and 1 from the North American and Caribbean Rugby Organisation. During the original domination, everyting was very much skewed towards the European type of game, but with the more recent domination of the Southern Hemisphere, the more physical almost brutal style of the All Blacks and Austraklians have become more important. With the arrival of the Japanese, Argentinians and North Americans where there seems to be a greater emphasis on finesse, things may change again.
Not sure what you would replace the 6 Nations tournament with. Are you suggesting that it should be cut so as to create a mirror image of the Southern Hemisphere's Rugby Championship?
I think that there is still a place for the Lions concept with, perhaps, more involvement, as the Baa-Baas perhaps, when entertaining a S.Hemisphere team i the UK. Should it include the French, perhaps?