I would like to see the card outline color change based on some date based criteria if a due date is present for the issue.
Overdue = card outline is red
Near overdue (user selectable date offset criteria) = card is yellow
Future due date outside of 'near overdue' criteria = card outline is green.
As I understand it, the whole point of a Kanban board is it's visual organization of tasks and swimlanes. Any way to present additionally helpful information immediately, without JQL, is going to be a bonus.