To go out and sign five 18 year olds from NZ is a big risk for a club to take. It's cheaper, and ultimately better for a club to instead spend that money on junior development in the local area. Not only will that produce players, but also produce fans too.
As to someone playing for England on ancestral rounds, well it's very unlikely tbh. It really would not go down well over here at all, I certainly would be very pissed off with it. And with the number of talented juniors beginning to emerge I don't see it being necessary anyway. It's the celtic nations and the like that look for ancestral links.
I think (hope!) there is a genuine realisation amongst the clubs that something needs to be done, and this is a way to do it, after all, it takes place slowly and over a period of five years, so clubs really do have the time to develop their own. many clubs already do have good juniors, some are starting to step up their systems, others have work to do.