Mandatory Due Date Switch
It's common practice to insist that a due date is set for an action when it is raised. However, it's not possible to mandate completion of the Due Date field for a particular tracker in Redmine. (There is a kludgy work-around of defining a mandatory custom date field, but the features associated with the Due Date field, such as Gantt and Calendar entries are then lost.)
Proposal: Add a mandatory Due Date check box to the Trackers>>Feature page (near "Issues displayed in roadmap").