I'm actually thinking about possibly using a motorized roll shade, like something from Hunter Douglas. Then replacing the plain shade with something I'd have custom printed. That would be fitted behind a panel so that it rests flush with the panel. The opening would be framed.

When down it would look like a framed picture of some sort and when open the TV would be seen, also framed, the panel and frame mentioned above covering the TV's own bezel. I'd make the whole panel assembly each to take out,by making it essentially a box that just sits on the shelf of the unit I'm building wall-to-wall.

The motorized aspect is kind of critical because I'd like to automate it with my remote, so that when I turn on the TV and source components, the screen is revealed. Then hidden when everything powers off.

This is all an "ideal" of course. I'm perfectly happy to just build out the whole wall unit and leave the TV visible at all times. This is icing on the cake and I'm sure my wife would really love it.

Here are some commercial products:

ArtScreen by Vutec

Art Lift by MediaDecor

This is definitely a high-priced niche market.