I am from a Game Server hosting company, and downtime is not an option. Granted, we have Techs in the DataCenter 8 hours a day, and an on call noc tech 24 / 7, we want to catch downtimes ASAP, and restore the downed server quickly and efficently.
Another thing I thought of is using socks to establish a connection with the FTP server on each box. Open a connection on port 23, and once established, closed. If it doesn't respond, either FTP is dead, or the box is down. I've been trying this, but simply lack the knowledge required. Again, though i'd ask here.
Thanks for your reply, though.