Multiple FTP servers with different characteristics on one server?

[Paul Hoffman]

To answer my own question:

inetd lets you run multiple instances, each one listening to a 
particular port, using the -a option. lukemftpd from the ports 
collection lets you give a directory for the set of ftpd 
configuration files.

So, now my rc.local file has:

/usr/sbin/inetd -wW -a 10.0.0.1 /etc/inetd-for-1.conf
/usr/sbin/inetd -wW -a 10.0.0.2 /etc/inetd-for-2.conf
. . .

/etc/inetd-for-1.conf has:
ftp stream tcp nowait root /usr/local/libexec/ftpd ftpd -d -ll -c 
/etc/ftp-for-1

and so on.