Logout to server selection screen.
Button on the ingame esc menu to allow logout to server selection screen.
I'll admit to doing this and I suspect I'm not the only one. Logging into Xsyon but selecting peace instead of war or vice versa. I often click through without thinking walk away to do something while the log in is happening only to come back and realize I logged into the wrong server. Or you're in, say, war finish what you were doing and want to log into peace on the same account.
Currently for both of these situations the only option is to hit esc and then exit the game. A nice option would be to have a log out button on the esc menu that takes you back to the server selection screen.