Possible to use only Group Chat?

Is there a way to somehow disable the IM part of Spark/Openfire? For our organization, we use Office Communicator for 1-on-1 communications - this is standardized through IS-IT, so there’s little hope of replacing it. We have, however, been approved to begin testing for Spark chat rooms.

To avoid any backlash from IS-IT, I’d like to be able to disable 1-on-1 conversations (or even just hide users). Is there anything like this possible?