This is really interesting. Temperance is based on the Baroque emblems of the virtue Temperentia, e.g. Cesare Ripa's Iconologia and his many followers. An allegorical female figure, tempering wine with water (and water with wine), embodies this virtue of finding the perfect balance. However, Colman Smith changed this image in significant ways and I think you are right, the apocalyptic angel must have inspired the changes to the image.