Just out of interest, I asked the Ali seller I got mine from if he'd ask Longse if it's possible to get a true 16:9 1920x1080 image with a firmware update. This is the reply he received:
the model's sensor is IMX178, please refer the character from Sony Webpage: http://www.sony.net/Products/SC-HP/new_pro/september_2013/imx178lqj_e.html.
Its "all-pixel scan" is 3072 (H) × 2048 (V), (1.50:1) , when you set up 1920 * 1080P (1.78:1), the image is being compressed. so the image looks not like 16:9. But it is nornal. so it can not be solved by a firmware.