Overall I quite like the idea - The only down side I see is that other than at a world cup there is no cross over between the different divisions.
Currently the likes of Samoa, Tonga, Georgia, USA and Canada all get 1-2 tests against the big boys in the November internationals.
It's certainly a better model. But I'm still not a fan of shoehorning the RC and 6N's into the structure as it still offers the same issues as previously regarding pro/rel and the 6N Unions. Even though there's a circuit breaker in the form of the pro/rel game I can see an all holy stink being put up if one of them looks likely.
I'd personally prefer them to look to implement this structure external to those structures. During the test windows. They could do this while keeping the two conferences but instead of 6 use 7 teams each and mix the conferences up more. That way the first stage would be northern teams travelling south in July and southern team north in November. Do the same for the 2nd division and keep the 3rd div as planned.
This would give each team 6 games in the NC and the RC (which could add whichever teams they wanted or maintain the current format) and 6N's can operate as is. This would eliminate much of the resistance to the concept in my opinion.
Regarding crossover games the only way to do that would be to have a 24 team 1st division with multiple pools/groups etc. Which would essentially just be the RWC on a yearly basis.