I have found it extremely hard (ie impossible) to get domestic award flights on LAN from SCL or EZE. I understand they sometimes appear, but I'd not assume that I could build a South American itinerary using QF FF points.

If you are considering a one way SYD-SCL and points for SCL-IPC-PPT-SYD, this may be a very expensive option compared with a SYD-SCL-SYD flight.

There used to be a good value South American air pass but I think this has been doscontinued.

The OW Global Explorer fare may allow you to "island hop" across the Pacific between South America and Oz. This should also give some South American flights that may suit.