I know that any similarities to Freelancer should probably be played down, but there was one thing that Freelancer did that was interesting UI-wise. Like vi, it had a modal interface. For those who haven't played it, you'd press a particular key (I think the default was spacebar) to toggle between a mouselook-style flight mode and a mode where you'd have to click and drag to turn. The second mode freed the mouse cursor to interact with other gui elements. It became quite natural to use after a short while. This ability might be incredibly useful in an RPG setting. Things like inventory management while still being able to see what you're doing, configuring weapon groups on the fly, giving orders to bots, are examples of things that having that mouse input would be useful for, and this is one way to get it while still allowing for mouselook-type movement controls (which are the present staple for 3-D interaction, and about the most natural way to do that right now).