10.20. How can I redirect service requests from one machine to another?

You can redirect FTP (and other service) request with the 'socket' package, available in the ports tree in category 'sysutils'. Simply replace the service's commandline to call socket instead, like so:

ftp stream tcp nowait nobody /usr/local/bin/socket socket ftp.foo.com ftp

where 'ftp.foo.com' and 'ftp' are the host and port to redirect to, respectively.