Gerber viewer feedback
There are many users who have problems and uncertainties with loading gerber files.
Viewer could give some feedback to user. For example - did it load the files correctly or something similar, because when it doesn't show some primitives, user doesn't know is it because of bad files or gerber viewer is made that way.
As example - I am not sure about board cutout - will the PCB be cut or not. Also I am not sure about the holes.