What if Hood was never completed and Tiger was heavily modernized to take her place?
Short answerTiger would probably be too worn and costly to rebuild, while Hood's absence could let Britain construct three faster 16-inch treaty battleships instead.
NotesRebuilding the worn First World War battlecruiser Tiger with 14-inch guns and modern protection would approach the cost of a new ship. Without Hood counting against Britain's treaty allowance, the Royal Navy might be permitted three new 16-inch capital ships rather than Nelson and Rodney alone. Those ships could follow a faster F3-derived form and reach roughly 28 knots. A pair of such fast, 16-inch-gun battleships at Denmark Strait would create a very different encounter with Bismarck. The counterfactual turns on how an unbuilt Hood changes treaty-era new construction rather than on making Tiger into Hood.