If you wanted to play Tankplank with extra slow, Frozen Mallet has been available for years, but that Gangplank was never particularly strong. When bruiser CDR options are better than ever, why would you build GP tanky CDR down the line? I could see some build order towards Warmog's, Cleaver, Frozen Fist, LW; or aether's suggestion of IE, Shiv, and tanky; but a Mundo build? No.