A channel for ally chat is on the list of stuff to maybe add eventually. A staff channel, probably not. What other plugins do you use which might be messing with chat (DynMap included)? I've had other similar reports, and it sounds more and more like a Bukkit bug. Particularly the bug which has Bukkit report all blocks inside specific chunks to be air instead of whatever they actually are. If you have any plugins which refresh chunks (like BananaChunk), that seems to trigger the bug more often than it would normally occur.