Hi Joshua,
Thanks for this suggestion.
I think the main blocker here might be that protocols like SFTP just aren't designed for quick file storage and retrieval. Depending upon the SFTP server, connection and authentication can take several seconds each time, whereas local storage or specialised remote storage solutions like S3 have no such delays.

Would it be an acceptable delay for you and your customers to add an extra few seconds wait, each time a remotely stored file is uploaded or retrieved? ie. every time a ticket is viewed by a client/customer or every time an email is sent with an attachment.