But even if you buy the extra coupons for the South Pacific area you still have the total coupon limit.
Usually it is cheaper to buy sectors in Australia on a seperate ticket. Check tavel.com.au. You can buy etix from them easily.

Also think of starting the ticket in IST or CAI.
I usually buy mine in CAI - lots of information here about this.
Turkist Airlines (not the worlds best) has good one way fares in Business from points in Europe to CAI.