Feature request: Panel: Display: General: "Mirror to all monitors"
This would be mutually exclusive to "span monitors" I think.
This wouldn't allow for customised panel options per monitor but that's such a pain already that I suspect this would be an instant improvement for most people.
Some items aren't allowed to be duplicated to secondary panels so I guess they would just not be duplicated?
A secondary/subordinate feature request would be for Window Buttons to only appear in the panel for which their window appears.