Armored warship designs largely ended in the 1930s, materials never progressed beyond various types of steel treated with surface hardening. If modern day engineers were tasked with building a ww2 battleship hull and armor with current day materials what would it be like? For arguments sake only the structural and armor parts are modern, for whatever reason the theoretical ship would still have 1940s weapons and face the same enemies the last of the armored cruisers and battleships did. The largest ships of this era fired roughly 1000kg steel armor piercing shells, at normal ranges they would impact at around 400-500m/s. Threats from underwater torpedoes were usually around 300kg of TNT exploding below the waterline.