So basically, it would be a guild were you don't have to travel at a guildhouse to join, and Generals assign you to them at their leisure?
I'm trying to consider how this would have been used in the BT invasion, for example, and I can't see how it could not have degenerated into a single campaign with everyone in it. You've basically replaced the realm-wide channels by an island-wide channel.
On other islands, you may get 2 or 3 groups, but that still will re-inforce immensely the groupthink. This will make powerblocs stronger (as if they weren't strong enough) and diminish the realm-as-a-team spirit.
I think, however, that some options could be valid. Scout report sharing, for example, or easier communication between marshals, or maybe cross-realm standing orders. But a full message channel does not seem such a good idea to me.
