Have done the very thing you describe here, using Rob Grabons articulating arm idea...with one variation.
The customer had a recessed shadow box built to within 1/4" all the way around the plasma...
We cut out all the drywall behind the plasma (it was recessed above a fireplace, so there was tons of room there) and got great ventilation...
Not only that, but it looked really trick when the plaster guys put some 45 degree corner wraps on the edges of the recess...when it was all said and donw...it just kinda flowed into this 3 dimensional FOCAL point above the fireplace, and looked great...the articulating arm was what made this install possible, as you can install them with very little clearence....
I have a picture of the before for sure, and possibly the after...e-mail if you're interested.
avdude
www.integrationpros.com