Can Mendix supply a FTP server on my Production Server hosted in the Mendix cloud.
No, because you would need to open ports etc. something that you do not want. From the Mendix side you can only retrieve using the SFTP module from the appstore. You can with Java reach a tmp directory in the cloud where you can do stuff. But I am not sure if you could create an URL to a file in this place. You might want to search in that direction to find a solution.
We saved or replaced the file in the web directory with a custom java action and pointed iframe to it.