Regarding your above plan to mount the screen on an adjustable arm, I don't think that will capture the true essence of what the majority of the people over the years have tried to achieve with their builds. Most have tried to achieve something that looks as OEM as possible or at least does not look like a Garmin GPS from Walmart stuck on the dash. I believe people that read your build will say "that's cool- a PC in a car, but I wouldn't want that big honking monitor stuck on my dash" then discount this as a quirky thing for only hardcore techies.
Having said that, I understand you want to focus on the PC build and not the audio or vehicle wiring however I think you could present a clean install without taking the build to an insane level of customizing the dash or pumping up the audio system.
By utilizing one of these to install the monitor:
or this if it is correct for your vehicle:
you would have a fast monitor install and position it as "it's as easy to install as an aftermarket stereo"
A small interface module for the Escape and a small amp that could mount right in the dash or a small PC amp and you would be fully integrated with a professional install without taking the audio system "to the next level".
This would also then give you voice navigation that turns down the audio when announcing a turn so truly an OEM experience. Pandora would be possible, satellite & HD radio, however far you wanted to take it.
Regardless of how you do it, thank you for noticing and spot-lighting our unique corner of the PC market!