Battlecruisers, pocket battleships, cruiser killers, and other similarly named battleships are fundamentally not designed to be part of a grand fleet with battleships of the same caliber, engaging in line-of-battle duels. Doing so not only seriously deviates from their initial design purpose but also exposes their fatal weakness in defense.
All designs that install battleship-grade main guns on a cruiser hull are essentially tasked with commerce raiding or counter-commerce raiding, focusing on maritime shipping lanes. At the inception of their design, the envisaged adversaries were mainly enemy cruisers or auxiliary cruisers. With comparable or even faster speeds, such warships could easily chase down the mainstay cruisers in operation, and using battleship-grade firepower, they could obliterate their opponents.
