That will look like a photo of a printout though. Seems easier to just hack the hardware to get it to sign arbitrary images instead.

ok but then the conversation switches from "was this actually taken from a camera" to "is this a photo of a printout" and we're not really any further along in being able to establish trust in what we're seeing, my point is the goal posts will always get moved because unless we see literally anything in person these days, we can't really trust in it