I asked a rep from orderinfinitiparts about adding these to my 2011.5 fx35 a month ago and got this reply:
To start, I, along with a few other knowledge bases that I have solicited, don't think there are AV jacks on any of the FX models anymore. This is in part of all of the demands and requests that consumers have sent to Infiniti through the past couple of years. Based on the requests and the progressive 2nd generation auxiliary reply to the requests, the AV plugs are disappearing and Infiniti is implementing the USB port in all of the models.
Yes, I do understand your concern, but I can guarantee that Infiniti never does anything to save on cost. Most of their initiatives are from a deeper rooted logistical engineering design. Infiniti strategic representatives have always said that they can't always explain "WHY" everything is the way it is, but can guarantee that there is a reason.
I have peered into the listings for the audio units for the S51 (2009-current) FX series and there are 22 different AV units and over 75 listings of application. Unfortunately, I don't have any way of ensuring what the empty plugs are for; however, if you provide me with your VIN, I can see what I can find.
The few things that I can reassure you of is: that the vague cut-out line for the AV port doesn't mean that it will work in the car, that may just the manufacture of that plastic "tub" attempting to cut down on their cost. I assume that rather than making a new plastic mold, they just use a filler for a hole that doesn't need to be there any longer. Also, the AV, USB, and any other wire that is in the console will route through the main body harness and not directly to the audio unit. Those plugs in the back of the audio unit may be for something that isn't there; however, these auxiliary components have always been routed through the body harness then to the audio unit.
As for the harness; yes, it will be quite pricey. I have always used a comparison of Infinities to my beloved Chevy Tahoes. I have noted that most manufactures like domestic companies will have the same harnesses throughout the entire car, regardless of the package or components that the car has. This leads to the possibility of adding individual components without having to do much more modifications. On the other hand, most foreign car companies have individual harnesses for each package that a car has. This leads to a difficult situation. For example: if you want to add a rear back-up camera to a car that doesn't have one, you would have to add the entire package that provides the back-up camera. We had some customers that did this years ago with navigation on the G35s; however, packages now have much more technologically driven components on them than before.
I do understand your mission with the video desire. The unfortunate thing of all of this is: that after enough concern effectively changed the port to USB, a company now offers a AV plug that is much more versatile for Apple devices, other MP3, and smart phones that could have circumvented all of the concerns.