OW services south of the equator?
 

We were planning to include NZ and OZ in a OWE and note that the choice of carriers really thins out in that region, and some of the Pacific island nations that might be attractive (Tahiti, Maldives, Seychelles, etc) don't seem to be accessible by OW carrier.

Any eligible code-shares, fifth-freedoms or second-label carriers or anything else I'm missing?

Interestingly, QF seems to have rights on at least one domestic NZ route, Queenstown-AKL, although they fly it infrequently.

British Airways has service to the Seychelles via Nairobi. You used to be able to go to Mauritius via Nairobi, but it is now a non-stop from London. You can get to Tahiti via Santiago with LanChile, but it's a dead end if you're on the Explorer. For the Maldives, you could fly to Bombay or Colombo then buy a R/T ticket to Male.

Seychelles is actually in the Indian Ocean, and is served by BA.

Qantas used to serve Tahiti, but dropped the service in preference for only running the codeshare. No dice on an OWE. Lan Chile technically serves Tahiti, though it would be a real big pain to actually use them because you would need to find your way SYD-PPT first.

You are correct that the Oneworld explorer leaves a lot to be desired in the South West Pacific islands. The Global Explorer, however, is good because you can also use Polynesian Airlines and Fiji Air. If I am not mistaken, with the OWE, you are limited to New Caledonia and Papua New Guinea.

Air New Zealand, while not OW, has a great intra-NZ network and a little thing called an Explore NZ AirPass that lets you fly around the country inexpensively. Basic price is NZ$515 (US$225) for three segments and NZ$171 (US$75) for additional segments (max 8). No OW miles but very reasonable fares for what you get. Note that you must book and ticket this from outside NZ and (this could be a killer) it may require you fly to NZ on NZ or a *A partner.

I agree with Darren. If you get a Global explorer you can do a LOT more in the South West Pacific.