After coming across some hidden bits in Communicator I created a simple app to enable you get edit 4 custom statuses inside of Communicator, as well as enabling/disabling "Appear Offline" as a status, and finally turning on archiving conversations to the "Conversation History" folder in Outlook.
The custom statuses rely on downloading an XML file on startup, which has to be done over a secure connection. Basically, because I'm hosting it, it means it could disappear at anytime. Also, the settings are stored on the machine, and not tied to your user account!
The registry settings that this app writes can be overriden with active directory settings so it may not work in that particular circumstance.
Anyway! It should work, but ymmv! Download here!
(Requires .NET Framework 2.0!)