I invert y-axis in first person, but in third person with a joystick i invert x-axis too. The way that makes sense to me is the joystick controls the orbit of the camera. I know this is insane, but like you, I'm also married to the idea. I think maybe it depends on if it's a shooter or an arpg like kingdom hearts where one joystick moves the character and the other joystick moves the camera.