if the characters are designed to be good or evil by default, maybe make alternate models to reflect which side they're fighting for during non single player mode (LAN or multi).
That would definitely be worthwile, but it could easily be done with a skinjob.
the buildings seem to me copies of the other side with only color change. i think slightly different models for each side would make for a more visually appealing expierence.
They are. I don't know if that'll last, but a slight difference might be good,