How does sysadmin delete submitted assignments?

Moodle 2.5

Hi
Moodle lacks the functionality to easily delete submitted assignments. This is very annoying since some of our students upload their assignments to the wrong link, and on top of that some of our teachers in their haste mark those assignments in the incorrect place. We are still struggling to find a sysadmin approach to this, that solves this.

This is such a simple core function for sysadmins that it does make sense why this function would not be included. 

Currently;

• Reverting to draft does not work.
• Deleting a submission causes a problem if the assigment has already been graded, since the mark will not reset.
• Sometimes a submission cannot be deleted.
  
• The explanation how to delete an assignment from https://moodle.org/mod/forum/discuss.php?d=83537 does not work and is heavily outdated but is still part of moodle.org nav tree (Right hand side of page).
• Two requests have been made by others;

1. https://moodle.org/mod/forum/discuss.php?d=268455#p1168392
2. https://moodle.org/mod/forum/discuss.php?d=263676#p1168395
   

Does anyone know how to do a manual delete, or if there is a fix for this that gives a tidy delete button next to a submission when logged in as an admin?