BTW if you choose to implement this feature I am willing to consult with you on how to do it. I have used a lot of task managers, so I know how easy it is to get this wrong. I would not have though so but I have seen it time and again.
Note you could use this to as well implement the "planned for today" feature that has 600 votes. Put them together, you have a lot of votes for this feature!
as i noted in the other recurring item request -- a repeat-upon-completion DOES NOT REQUIRE a due date. If there is no due date, the recurring task "just shows up" in your task list after the recurrence time.
Example : clean coffee maker every 3 months upon completion.
If I complete it on April 2nd, then I do not see a "clean coffee maker" task in my lists (except in the "scheduled" section ... which is where not-yet-startable tasks go). On July 2nd there is suddenly a "clean coffee maker" task in my list.
Repeating events based on completion ... note, these events DON'T REQUIRE A DUE DATE!!
The idea would be that these events show up in your task list, N days (or N weeks, whatever you liked) after the previous one is completed.