I have added the option to the admins of the site when editing a card to duplicate it instead and insert it as a new card. This way we can create new cards that are very similar to previous ones in the same set, we just edit the similar card, change its number, which needs to be unique, and any other differences, and the card is created with the data provided.
I have just used it to add the Ultimate Rare and Ghost Rare versions of existing cards in the YuGiOh Crimson Crisis set.
Also, when uploading card images, I have added an appropriate error message when the zip file is too large (or corrupted).