So many of them require a socket hole in the roof rail like my Taurus SHO does.
This is also where the power comes from for the vanity mirrors.
I was thinking of replacing the vanity mirror with a flip down tv monitor screen for a back up camera. It could double as a night vision screen for when I'm running in the stealth mode at night for those 220mph runs.
I would have presumed that many have done something like that already.
Of course perhaps my perspective is limited and perhaps most have updated to a weapons screen in the windshield like the F18 uses? Then they don't need to do anything with the visors. Yep, that must be it. That makes sense.