We're not sure what you mean when you say access to the light meter. There is no method to change the operation of the Auto ISO on this camera. We regret any inconvenience that this may cause you.
Full Manual mode assumes that you have predetermined all your exposure information; ISO, aperture and shutter speed.
Using Auto ISO removes your ability to control the ISO speed. If you want to use a specific ISO for certain shooting conditions set it manually and then manually adjust your aperture and/or shutter speed as needed.
I don't know for a fact, but I suspect your camera may allow you to pre-set a maximum speed when using Auto ISO if you're worried about the camera having to set a higher than desired ISO.