I have an idea about trading in GalCiv2.
First, their would exist automatic trading between your planets in the starsystem auto than if you wanted to gain more commerce, you've have a Starbase in both sectors, or built a structure on one planet or more in both starsystems and than you gain Galatic-Trading, Interstellar, whatever.
The graphics are for trading in your Empire starlanes. Floating self-batteried glowing lights on tiles and between them are a train of cargo, commerical and civilian ships to be precise, going back&fourth. Trading with other Empires is simply several lights in the row from your planet to one of theirs. The ships are less present but makeup with more heavy'en'larger commerical spacecraft.
If your Trade with another Empire is attacked, the starlane immendiatly halts, light graphics bright down than disappear, the commerical craft disappear or halt, explode, whatever. If starlanes between your planets is disrupted, it really only affects the economy of those planets. They'll suffer morale, weak population grow, etc. So Ships should be capable of blockading planets!
