We are contemplating switching our business site over to a WP blog system and in a discussion we thought it would be great to have an FTP upload system for our clients. All of the available FTP solutions are all about managing WP, but my idea is to have a plugin that added a login and folder control right there on the pages. We intend to use something like File Thingy and a link, but a built in solution would be better.
My idea would be that each client has a folder they can upload to. They would only see their folder, and we would get an email that said they had uploaded something. We could also drop things into their folder for them to download.
Based on MyFTP or a few others, this can't be too difficult to do, although I am not able to do it myself. Just an idea.