Especially in 6-inch phones like in this case, the cameras could definately be closer to te center than in smaller phones, even with a respectable battery inside.  Either by placing the battery on a side a la iphone 6(s) or making it more squarish.  The 5.5-inch OnePlus Two managed to place the camera quite nice, and the 3300 mAh battery sits relaxed away from any edge of the chassis...