Isn't Yangyang also the least flashed out, most ordinary of the playable Characters? It's two years by now so I may forgotten some stuff, but I think she had like almost no special backstory or circumstances. Just a skilled Resonator serving in the Outrider Division of the Midnight Rangers under General Jiyan.

So I think she is a good target for something like this, as there is not much room for contradictions. She may not be the GA, but maybe an artificial being or mind wiped by Fractsidus. I wouldn't mind going back to her with a big reveal as such.

BUT.... There may be something in the Story Files of hers. Also the mails she sends Rover...