That's an excellent idea for the VX and was very popular with the VW crowd about 13 years ago. I used to be big into Karmann Ghias and had one client who did all the lenses flush with the body. I believe it was clear lexan that had dark window tint on the inside that matched his gloss black paint, but had bright enough lighting that you could see it in the daytime and at night it looked as if the metal was lit. Another client had done something similar, but on a white Ghia. Again, all lenses were flush (except headlights) lexan but painted to match the body with the exception of small areas the size of a pencil lead that were left clear. At first glance you couldn't see anything but if you new where to look you could just make out the clear dots. The daytime visibility was poor but the effect at night was impressive. The owner of that car trailered her Ghia to shows, so I'm pretty sure she didn't risk getting ticketed over the "look".

I have seen prototype taillights that use fiber-optic cable and lasers to do something similar though. It would be pretty easy to shave all the lights (except headlight) and put in fiber-optic. All you would see is smooth finish until the lights came on. You could use off-the-shelf laser modules for the tail/brake lights and high-intensity LEDs driving the amber marker fiber. The engineering on such a system would be very simple and, with the exception of the bodywork, could be done in a weekend. The major downside I see would be the loss of reflectivity, which I'm sure will get you into trouble on a street car. But for a show ride...