To be honest, you should dream and I admire you for having such high aspirations.
There haven't been many All Blacks in the past that didn't play rugby their whole lives in New Zealand, but there is one notable one, and that's Greg Rawlinson, a born and bred South African. What you hear about proving grounds however, is extremely true. From under 9s right the way up to seniors, there really isn't a way to describe it. I've officiated a couple of under 9s tournaments in New Zealand and even the way these kids play is fantastic. Imagine, at 9 years old, trying to take quick lineouts, mauling properly, kicking to touch, trying to steal ball, offloading. It boggles the mind. I was playing in Rotorua for a while for under 21s Kahukura and I've never played such a violent match. In two degrees. With hail. The only way to find out how you fit in is to come over in the middle of rugby season and play around now. At 17/18, if you go for the first time to play for Christchurch University, it's extremely unlikely you'll ever see the field, because the level difference is such a huge shock. A lot of kids come over from the UK, the big fish in the small pond type. And they get much, much, much more than they bargained for. To be honest, it IS quite daunting, it's discouraging, it's brutal and some days will make you never want to pick up a rugby ball again, but you keep keep going, and those are the guys that become All Blacks. There are fantastic players all around New Zealand, absoloutely fantastic, but the difference between those that get npc contracts and those who don't, those who get super rugby contracts and those who don't, and those who become All Blacks and those who don't, is how far they're willing to push themselves. I've seen some players that could easily be playing npc, but they're not willing to go through what others do to get where they are. If you can survive the proving grounds, you're in with a shout of squeezing you're way into super rugby.