Re: Recommendations for private cloud software...
A few UK universities use a variation on the original Perl UD Dropbox software to allow people to drop off and pick up large files.
i.e Julian Fields, creator of MailScanner, has released "zendto" which sounds like a better fit for your needs. It's open source, so if it's not quite right you can hack away to make it work.
http://www.zendto.com