Alternately, Yamamoto might ponder soberly what he is learning about the garrisons and air forces on New Cal and Fiji, the long supply lines and distance from his Solomons air bases and the imponderables of American reinforcements to the Pacific, and decide instead to pile the extra Java troops into whatever he has seized in the New Hebrides, to dig in and fortify. Perhaps hoping to use them as bait and reconn for any Nimitz counterattack.
Ultimately that is the smart play. The further they extend the defensive perimeter the harder it gets to defend or even supply on a day to day basis.
I still think Port Moresby is the smartest play, but if I had to stage FS, I think this might be the best way to go about it.