I don't think I can overstate the importance of NOT being able to edit hidden layers. I have years of experience in digital painting and editing and I still forget to switch from a layer I've hidden once in a while. ops: The ability to undo makes what would otherwise be a disaster into an annoyance, but the slow down in work flow is enough to make me post my peeves. I realize I'm asking you to protect me from my own inadequacies but there it is.
I don't think I can overstate how much I love ArtRage too by the way.