Not to be a traitor to Oneworld (since I'm a BAEC member) but if you are buying tickets with your own $, *Alliance might be a better option, at least for some trips, because there are several carriers with premium economy products on the trans-Pacific route, while Oneworld has no PE routes across the Pacific (someone correct me if I'm wrong about that). With *Alliance, you've got at least Air NZ and Thai, and also possibly Singapore Airlines and ANA. (I think there are a few BA flights from Sydney to Singapore and Hong Kong, as part of Oneworld.)

On the other hand, if you can organise your trips so that you make stops in several countries, a business class circle pacific ticket in Oneworld might be a decent value.