In 2011 they offered a Cedar/Macassar Ebony 12-fret GA Limited (very limited, like 40 pieces). I bought one then and LOVED it immediately. I later built two additional Customs as 12 Fret GAs as well (Redwood/Figured Rosewood and Englemann/Quilted Maple), and think this is a perfect configuration. Not sure why it's not offered in the standard line, doesn't seem to require any additional tooling.
Thanks so much for posting! Truly stunning, all of them. I especially like the Redwood model.Pic of my 12-fret GA below: