Message Audit Policy type flag filter

My boss just asked me if broadcast messages were logged so we could use those to track events effecting multiple users. I looked into the audit policy and found that while I could turn this on, it would also log every word sent by any user regardless of whether it was a broadcast or not. I noticed in the XML that broadcast messages has a flag set for broadcast and I wondered if it was possible to add a Message Type check box for broadcast messages only to be added to the policy manager. I’‘m all for preserving message privacy, but can’'t we have it both ways?