As I recall, sheepheads do something similar (largest and most aggressive female becomes male). But... and here's the thing, they appear to do it purely to mess with the researcher's heads. While I was volunteering at the Monterey Aquarium, there was a story that the rule they had worked out was "largest female becomes male, only 1 male in an area, no backsies." Then the second largest female started to transition, and became male. Then the two males got on okay with each other (they fought more than they had, but they let each other live). Then the smaller one transitioned back to female.