Read and write files from external FTP server
I think you better face this problem using system commands that adding FTP support to the Drupal stack.

For this you can use:

1) standard FTP. You can read here how to automate FTP commands from a bash script:
http://www.stratigery.com/scripting.ftp.html

2) SFTP, FTP over SSH. If you can use SSH public key authentication this is the best way as you only will have to exec this command every day:


scp your-remote-user@your-remote-server:/path/to/files/* /local/dir/for/files


Once your files are copied locally you only have to process them with Feeds.

You can even use PHP exec and launch the script that retrieves your data from the Drupal Cron.