They could re-implement the Light/Dark tree very easily. It could be based on your actions, whether you use your force powers for good or bad purposes, and how you accomplish different objectives. There should be several different ways the game can proceed after each level depending on how you accomplish certain objectives. So it could be quite easy to re-implement it. I completely agree with you about water, but I hope it's realistic to at least a certain extent.
"Shut up Arcturus, if I wanted your damn opinion I would have beaten it out of ya." - Former Marshal James Raynor