How would Azur Lane shipgirls fit into the Royal Navy's chain of command?
Short answerThe normal structure could absorb them: operations belong to the First Sea Lord, personnel to the Second, and procurement, engineering, dockyards, and maintenance to the Third.
NotesFictional shipgirls could fit within the responsibilities already divided among the Sea Lords. The First Sea Lord coordinates operations and the fleet overall. Personnel matters fall to the Second Sea Lord, while procurement and design lead to the Third. The Third Sea Lord's dockyard responsibilities also bring maintenance into the same division. A character embodying both a person and a ship would approach different offices according to the issue.