I have STC approved a number of cameras on aircraft, it's not that big a deal. One of them saved us from a one gear up landing in the DC-3T once, as we used the camera for its unintended use of visually checking the right gear, and seeing a ski check cable snagged in the axle. with the camera, we got it unsnagged, and the gear down. That said, the cameras I have approved were intended for use in flight, rather than taxiing. It would concern me the distraction of eyes out/eyes in looking at a camera while taxiing. Eyes out is by far the most important, for obvious reasons!
There are times I decline to approve something, or restrict its use, not because of the system itself, but rather how it may be used, and create a distraction for the pilot at a critical time - a camera for taxiing in a single pilot airplane is in this realm if consideration.