I think Fallout 3 had a mod that did this. Basically, any message that requires user input and stops the game flow - like DLC added messages, or "PRIMM SLIM HAS DIED!!11one" messages - move them to the upper left. Simple, and makes the game a whole lot less intrusive.
If there is a simple way to do this, teach a man to fish and I will gladly apply it to all the messages myself.