Why the Courageous conversions were a tolerable treaty outcome

Were the three Courageous-class carrier conversions the least-bad treaty outcome for the Royal Navy?

They were imperfect but useful experimental carriers whose age also allowed Britain to replace them when newer designs became available.

The Courageous-class ships were imperfect carrier hulls, but conversion gave the Royal Navy useful aviation capacity. They were not much older than the American and Japanese conversion candidates named in the question. Their experimental status also allowed replacement when Britain wanted newer ships. Expectations of another major war made that flexibility useful: the conversions provided something to operate while leaving room for a later generation.