OK first off, yes this was sparked off of battle.nets launcher chat, but only because its a good idea.
I would like to see ESO's launcher have a built in chat system that allows you to talk to people even when they are not online in game, but are signed in on their launcher, and also allow people to talk to people cross platform.
This would be helpful because it would help friends contact each other to play ESO and other games together, help guild members find each other for events and or remind them of upcoming events, and help break down the social barrier between console and PC gamers, allowing the ability for friends who are cross platform the ability to still communicate. This could also potentially widen the mail system to allow cross platform mail, which could in turn help expand trading guilds as they potentially go cross platform with the use of guild websites.