While Googling a bit on oddball freighters ran across this. The world's first commercial submarine, the Deutschland. If someone wanted a unique boat for campaign play, this would be one. She'd be 18" at 144:1 scale. Wide design should turn well.
Heh. I-402 was redesigned partway through construction, and was launched as a giant submarine oil tanker. She lost her catapult and aircraft hangar and got a balanced, more compact sail. She also retained her torpedo tubes, but ditched the reloads. Not sure about Fast Gun, but she's definitely legal in most Big Gun clubs.
USS Argonaut and sisters are legal convoys in IRCWCC, as they were specifically converted to troopships (Makin Island Raid).
I-402 would be legal as an IRCWCC convoy ship but I don't know if she'd (or the Argonaut Class) be allowed to dive.
