The case you are describing seems easily solvable. Setting-up a cronjob, running as frequently as required and checking in a particular directory (filesystem or content tree) for new image files (they will have to be named sharply, letting the system identify the associated article), and populating existing articles with their respective images would be one way to achieve this.
The other way is, as you guessed, letting editors edit the already existing articles manually (like any content edition) and add the new images.
I hope this helped you,
Let us know if you have other questions, Cheers,
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Nicolas Pastorino
Director Community - eZ
Member of the Community Project Board
