Hello, I have a few ideas:
1) Have a page on the Hostony site with the current status of the different servers, the current notes (if it were down, the cause and what is being done about it, etc). You can check for current and/or future activities. My webmail for my ISP does this (http://support.cox.net/networkstatus/index.jsp) so this would be a nice addition. Instead of states (as in my example), you could post the different servers.
2) Create not only a Hostony Mailing list, but also a mailing list for each server. The customer can then go and sign-up for mailing (probably thru CPanel to make it easy) for their server. There can also be a check box or something for the Hostony mailing list as well as the server mailing list. This way if there are planned outages/work to be done, you can contact your customers easily. With that, if something were to go wrong, you could contact all of them immediatly stating that there is a problem, what the problem is, and what is being done about it. Since many problems with the servers cause the email to go down, possibly ask for an email address (required) and an alternate email address (optional) to email both places in case a customer is using a website email for contact, and the email system is down.
Just my 2 thoughts!