Translated node references same file attachments

When translating a node with file attachments, the translated node references the same physical file.
If the file is deleted from either node (either manually in the case of file attachments, or by uploading a replacement file for single-value CCK filefields / imagefields / etc), the other node retains the file link but the physical file is naturally missing. This causes a discrepancy between the data and the file store and, further, is not the expected result.

As Drupal 5 does not support files being shared between multiple nodes, the expected behaviour here is for the file to be duplicated (renamed to eg. filename_0.xxx) at the point of translation.

Given that this is Drupal's normal behaviour when encountering a file with the same name, it seems the easiest way would be to make a temporary copy and tell the system it was uploaded by the user - but unfortunately I don't know how to achieve something like that.