As I can tell from the UOR website there are a lot of people now in factions. I think everyone could have a place in faction and be informed when and where a fight is happening with a Faction Chat. Just like how current guild chat works but for a whole faction. I think it would be fun for new players who want to faction to know where a fight is taking place and or if we are going to attack a base etc etc.
I don't know that anything like that existed before, however, I'm pretty sure the leader of each faction has the ability to send messages to the entire faction. Aside from that, there is intention (however long term) to implement Alliance chat. However, as I understand it, this is tied in with larger scale changes to the function of guildstones and the management of the guild itself as well. For example, you can't even set an alliance right now and the guild master's gump doesn't show guild titles within it. All told, there's much to be done there but I think in the long run, Alliance Chat will suit your desires as you can align with whatever guilds are in your faction, if you so choose.
Well if you are going to all fight together, couldn't you like, be in the same guild? Seems like the whole idea of "guilds" has been basically lost, and in current serves only as a way for you to post funny titles over your head across all 15 of your characters.
Not everyone in a faction wants to be in the same guild. We fight for the same cause but guild membership provides tangible differences in looting rights and criminal flagging. I'm not going to just guild up every nerd that joins SL simply because they have the robe. Guilds are highly useful for communication, combat training, adventuring (looting rights, etc) and of course, silly titles.