If you guys are making some serious cash with your PPC/IM stuff and really care about security you should be able to find a competent admin that installs you proper BSD jails: FreeBSD jail - Wikipedia, the free encyclopedia. Should beat any other virtualization solution if used with ZFS. It's on my TODO list to play with this stuff...
I can't really tell if it would help all that much from a security point of view apart that it would probably prevent brute force password login attempts, but I've hidden the login page and replaced it with a dummy login page.
You can enter passwords all day long but nothing is actually being processed.