Allow more finegrained control over submitted filenames in collective zip download of assignment

Currently, the "Download all assignments as zip" functionality modifies the filenames of the students submissions using the scheme

firstname_lastname_filename

Our teachers have reported some issues with this hardcoded way to modify the filenames:

• The induced ordering by the students firstname is extremly inconvenient (and somewhat illogical for many languages). The ability to (optionaly) change the ordering to lastname_firstname would improve the situation a bit

• In some use cases, teachers instruct their students to stick to a specific naming scheme for their submissions, especially if additional information should be available at first glance in the grading view. Even if all submissions stick to this scheme (and therefore no renaming would have to take place), the download script still prepends filenames with firstname_lastname , resulting in very long filenames containing sometimes redundant information.

• The used way to automatically rename all files upon download as zip raises concerns about collisions of generated filenames for students with identical names (some of our courses have ~1000 participants and some names are very common in german)

I would be very grateful if you could consider improving the (very welcome) functionality of "Download all assignments as zip" in either (or all) of the following ways:

a.) Allow configuration of the generated filenames in the ZIP file for download on a per-activity basis
b.) Additionally, it would be nice if fields beside firstname and lastname could be used (e.g. username or custom fields with the student ID are IMHO better suited to identify students contributions uniquely)
c.) Optionally, allow to disable the renaming of files (+ throw exception / display warning if filename collisions in a downloaded ZIP file would occur)

This improvement request shares ideas with http://tracker.moodle.org/browse/MDL-29343 (Separate folder for each students work).