Is there any conclusive evidence to prove that 12 rounds is any safer than 15 rounds? I doubt it. I doubt it's any safer at all. Perhaps I'm wrong, but I've always thought the demise of the 15 rounder was more to do with TV networks wanting a more condensed package (and thus having more time for other stuff) than it was an issue of safety. But whatever the reason, the 15 round fight is the way to go.
In what way was it recognized ? And at what weight was it set ? British used to call the 175 pound division cruiserweight or light-heavyweight, but I know nothing about an extra division.
The junior welterweight division is the clearly obvious exception, as it has long since established a storied tradition and legacy lacking in the weight classes created since. Only Duran has snubbed it in modern times. (Seeing how Roberto did against Cervantes at 140 would have been interesting. Unifying the light welterweight title when only the middleweight championship remained undisputed could have been a nice additional feather in his cap, and we might have been spared his dismal showing against Zeferino Gonzales.)