Well spotted craig , the dension unit can cope with all the audio inputs that i am ever likely to require and i would need to use an lvds break in box for the video input. There are a couple of these units i have seen, Dension have one under development.
Q7 / MMI | NAV TV - Leader in OEM Video Integration
http://www.navtv.com/manuals/RGBA8/RGBA8.pdf
Even though this is not a perfect solution due to the additional packaging requirements it is definitely more cost effective than using oe equipment. Some of these units contain a valet swith so any DTC's are not detcted by the delear, however i would prefer if the software was developed to prevent a dtc being logged in the first place.