Good point. I think it’s probably cheaper to build a ship than fill in more landfill to expand the resort. It also lets them build off the existing investment whereas building somewhere else in Japan, like the Fukuoka plans OLC considered in the past would be in competition with the main resort.
This is really a good time for OLC to capitalize on Ogasawara Islands to make it ala Castaway island or partner with Okinawa Prefecture to boosts tourism and funfact OLC already has a non Disney Hotel within the Island.