I've deleted all of the replies to this thread and I'm starting over. I think Jason misunderstood your first question and was taking you down the wrong path.
Go ahead and delete the hidden form elements he had you create.
The way to get the file upload fields to keep the values from the database when they aren't updated is to set the "Default Value" in the upload server behavior to the current value from the database.
The default value is what is used when no file is uploaded. If you set that to the current value from the database, then if no file is uploaded it will keep its current value. You shouldn't need to add any hidden fields, or adjust the update database table server behavior. The correction can be made in the individual file upload server behaviors.