Self shadowing is a waste of time, in my opinion. My three big graphical 'wants' are The ORB, 2d/3d cockpit support (with a change to the HUD code to allow HUD panels to be placed with pixel-level precision) and on-demand overexposure (ie, you can have windows on a hull overexposed and nothing else).
In the realm of non-graphical improvements, I'd like to see a revamp of the physics system (I can dream. I want a rules-based pluggable physics system), a full on scripting layer (which would replace, and implement as a subset of its functionality, all SEXPs and have access to all systems and objects inside the engine), user modifiable subsystems, and hot-pluggable mods.
I don't ask for much, honest.
