Not sure how it would look, but after looking at your pictures it looks like you could mount a pod on the dash above your vents that curves around the front of the dash.

By creating a pod that also curves under your dash, you could hide the ribbon cable and run it behind the plastic facia where the vents are. You could use some small screws to hold it in place or velcro strips.

I'll upload a couple of sketches to give you an idea of what I'm talking about. You might be able to make some of it from wood, but you might take the foam, bondo, wrap with vinyl route.

Maybe this will at least start some ideas for you.

BTW - a profile gauge helps gets the curves correct. http://www.fine-tools.com/G309631.htm

Mark