CSV Update: provide a way to update a list of issues through CSV import

CSV Import is a great feature but only allows to create issues, not to update existing issues.
Jelly Script is another great feature but there is no available documentation on how to update existing issues.
The Bulk Change allows to update a list of issues but the new values of the updated field has to be the same for all the issues in the list.

We need to be able without messing with the SQL data base to update a list of issues from a CSV file that would provide the new values of the updated fields.