Is there any plugin in Directory Opus to directly upload a file to a file sharing host and get the URL copied to clipboard.
Just like the way I have my account for ImageShack configured in the settings, I can simply select any image and push the toolbar button to upload it and get the URL.
If the host lets you upload using FTP or SFTP then it should be fairly easy.
Or if the host provides a tool for uploading files, that may also be fairly easy (depending on the tool).
But if the files have to be uploaded via a web browser and a custom websites, which nobody has written a tool for talking to, then I expect it will be difficult.