The large I-400 hull offered useful volume beyond its aircraft mission. The design could have been adapted into a long-range minelayer, while I-402 was intended for conversion into a submarine tanker, or milk cow. Both alternatives exploited the hull's unusually large volume and endurance rather than its aircraft hangar alone. A common large-submarine design could therefore support strike, denial, and fleet-logistics roles across the Pacific.
Notable Point · 34:59-35:27
A large hull could support minelayer and tanker variants
The same range and internal volume that supported aircraft could produce long-range minelayers or submarine tankers for a dispersed Pacific campaign.