Do you see any problems with this method of sending messages out to all active users?
At face value it appears like a very simple way to reach everyone who is active on the network, but your familiarity with the code base may yield a better alternative.
Alert protocol is perfect for this situations, it is fully implemented, except that the messages are not shown on the GUI.
Contract messages are not, but only a little work is needed to get them done. But Alerts are better: they work across forks.