Further to my reply to Scott T ... A fairly straightforward design adjustment to accommodate my needs would be that when a recurring task is marked as complete, Evernote doesn't immediately update the due date on the repeating task, but instead proceeds in two stages:
1. It clones the recurring task, setting the clone as a non-recurring task with its due date set to the current date of the recurring task (i.e. the as yet un-updated due date) and with a status of completed.
Note: If the user ever comes back and marks this completed task as incomplete, then (provided no later occurrences have since been completed), the recurring task due date is set to the due date of the clone, and the clone task is deleted.
2. It updates the due date of the recurring task to the next due date.