If Britain built conventional battlecruisers instead of Fisher's Courageous-class large light cruisers, which hulls would become treaty carrier conversions?
Short answerBritain would have to use whichever conventional capital hulls replaced them, most plausibly an Admiral-class or G3 design available when the treaty conversions were chosen.
NotesCarrier conversion depended on which large, modern hulls were physically available when treaty limits stopped capital-ship construction. If conventional battlecruisers replaced Fisher's Baltic ships, Courageous and Glorious could not fill that role. The Admirals or G3s then become the plausible British candidates because their size and construction timing place them in the relevant pool. The result would be a much larger carrier lineage derived from genuine capital ships rather than specialized large light cruisers.