Does a modern navy need an arsenal ship carrying many more cruise missiles?
Short answerPossibly, if defensive weapons consume the launch cells on ordinary combatants, but the requirement is much stronger for a large US fleet than for the Royal Navy.
NotesAn arsenal ship is a conditional solution rather than a universally necessary class. If escorts must devote more of their launch cells to air-defense missiles, a separate hull could carry the fleet's opening load of land-attack weapons. That division preserves strike volume without weakening the defenses of ships expected to survive close to the threat. Whether it is worthwhile depends on the navy: the US fleet may find a use for such capacity where the smaller Royal Navy might not.