Rode the Croesus track last weekend on the West coast of the South Island NZ. Most of the parks there are Forest Parks so seems they are all rideable. There's a whole heap of much more technical terrain available. I think it's definitely a destination to look into but weather would be a huge deterrent - it is the wettest place in NZ. Apparently when wet some of these are un rideable. NZ is really world class in terms of alternatives now. They have apparently just finished the Taupo trails - that's single track around the whole of Lake Taupo. It's a pretty easy long weekend too.