Maybe the size of the local chat and shout should just be expanded so that when you are in any given city, you can basically hear all the chat that's going on, since right now it seems like the distance on say and shout are pretty short.

A global chat channel might be nice, though for me it'd have to be something that you can choose to turn on/off for reasons like the example that indira has posted above. In some cases a global chat can just be way too spammy.