As Maxwell Everett has shown, you can crop the show and none of the production elements would be any more visible than they were in the 4:3 presentation.
While it's true that CBS-D has had to, on occasion, erase production equipment from certain shots or even subtly reframe shots in certain cases, my examples show that a 16:9 version of TNG would be even wider than TV Transmitted, so even more objects would be revealed, causing an even bigger headache for CBS-D. Again, go to 3:44 in each video and take notice of the white bounce board that is visible in 16:9 but not 4:3.
I'm afraid that I threw gasoline on the fire here. In any case, one of the primary reasons they are sticking to 4:3 is that in many of the filmed miniature elements the guys at Image G were sometimes framing using the full camera aperture and there simply isn't anymore image left to reveal! You've all seen this video from the Energized! doc... look at the rounded corners in some of the Enterprise elements -- that's a hard matte in the camera, there's nothing left to show!