Daru to is a possibility and that would be an absolute nightmare for both Australia and Indonesia. Jeez if Japan had managed to build a Rabaul or even a Weewak type of base at at Daru, it would have made life at Darwin extremely difficult. They would have had control of the Arafura Sea and basically cut Darwin off from air, sea, and probably land support. I know that RAAF B-24 bombers operated out of the Pilbara against Japanese targets in modern day Indonesia, so they could easily reach Daru from the NT outside of Japanese aircraft strike range.Manus Island has been of interest to Aus and the US for some time, and there was a project to upgrade facilities there for our use although I’m not sure where that is at. A more worrying possibility might be an upgrade to Daru (which it badly needs btw) so as to “properly support the fishing fleet”, enabling it to be used. Possibly without PNG approval; in a conflict situation China would probably regard that as irrelevant. Imagine if Japan had had an airhead at Daru in 1942....
The RNZAF, RAAF, USN and USAAF were still bombing and strafing Rabaul right up to wars end. Think there were 100,000 Japanese bottled up there.