Just sitting & pondering more for you..Please don't limit yourself to the South Island

What about renting a touring van (kea campers?) and doing some tracks in certain parts of the north & south island ??

1-The Colville Connection www.colvilleconnection.co.nz

2-The Karapoti classic near Wellington-you can do the course outside of the actual event day

3-Mtn biking in the Rotorua region & beyond..

That's all i can think of..must go to bed..

c