This flag is suitable because it is, in a way taking the existing flag and updating the union jack with our national icon the silver fern, which represents us as a proud individual country and no longer a far flung British colony as the current one suggests. The southern cross remains as it is an important part of our flag and anybody fifty years ago could then recognize this as being a New Zealand flag due to this similarity. And what better way to symbolize our nation then replacing the blue background with our national colour, black. This flag stands out with red and white contrasting black and represents us as a nation with our national symbol the silver fern.
Silver Fern: http://static2.stuff.co.nz/1318812234/005/5799005.png
Southern Cross: http://i.imgur.com/vapAeYt.png
Fern designed by Dave Clark