Hi @inkedmn:
What you are looking for sounds taylor-made for Amazon S3 as a hosted file service to complement your client’s web hosting. It’s incredibly cheap (my S3 bill is currently US$0.01 per month, but only for a few files) and has all sorts of content protection features like special expiring URLs and so on.
I wasn’t able to find a plugin to do exactly what you are looking for, but you might be able to cobble something together from the features of several of these many Amazon S3 plugins:
- http://wordpress.org/extend/plugins/amazon-s3-url-generator/
- http://wordpress.org/extend/plugins/wp-s3/
- http://wordpress.org/extend/plugins/tantan-s3/
- http://code.google.com/p/wordpress-s3/
- http://www.blogperfume.com/plugin-automatic-wordpress-backup-to-amazon-s3/
- http://www.wizardstower.co.uk/wordpress/2008/10/25/amazon-s3-plugin-for-wordpress/
- http://photocritic.org/wordpress-amazon-s3-cdn-plug-in/
- http://imthi.com/wp-s3
- http://tantannoodles.com/toolkit/wordpress-s3/
You also might be able to integrated with WP-File Manager (or even just use it):
It actually sounds like a super-fun project; I’m jealous. I need to get one of my client to need something integrated with Amazon S3! 🙂 Good luck!
-Mike