Would a 13.5-inch HMS New Zealand be even more formidable given her wartime reputation for luck?
Short answerThe joke adds heavier guns to the ship's established reputation for surviving danger.
NotesThe counterfactual joke gives 13.5-inch guns to a ship already famous for extraordinary luck. HMS New Zealand is imagined emerging from heavy fire with scarcely a scratch. The humour extends to a proposal that other Royal Navy ships should receive blessings from communities around the world. It draws on New Zealand's reputation rather than claiming that heavier guns would improve her protection.