The ability for characters to cry. KOTOR 3 can be the first game to genuinely appeal to the characters emotions. Keep the fighting system, and improve the graphics to show emotions, real time saber lighting ect.
What I would really like to see is something amazing. Something boarding DBZ style. Only slightly. The 'force' as we know it has not even slightly been tapped into. Someone who is really a master should be able to move planets, ripp spaceships appart. Be constally surround by red/blue auras. Eye pure white or black.
If you could do that then you will have something special.