IMO, the problem isn't really with the domestic set up per se, more to do with player development, cricket at a junior level and the pitches (not so much).
NZ is a rugby nation. Cricket is the summer sport that is followed but not as seriously as it should be. I'm not to sure what the current youth system is like, or if there is a national program. If there isn't one, there should be one. And if there is one, it needs to be stepped up.
Obviously, most prolific cricketers started playing when they were young, so this is where there needs to be a big focus. Shake the game up at a primary school level to make it A) more accessible and cheaper B) more enjoyable.
For Primary School, I think Twenty20 tournaments between schools, districts and provinces and age groups would be fantastic. Then in high school, upgrade to 40/50 over matches and then for seniors (i.e. 17/18 y/o's) have multiple inning multipe day matches. Have an U-19 competition that mirrors that of the main domestic comp i.e. CD U-19's vs Auckland U-19's at the same time the senior team plays. They could play the the provinces secondary grounds while the main teams should definitely play on just the main ones.
Basically, we should get in "early" to develop players at a younger age, rather than trying to quick fix the current competition to try and get us short term test players.
Unfortunately I don't think anyone is willing to invest enough money that is needed for it.