I have to say that I love the idea of having the attack and defence fall into 3 catagories of weapons tech because I finally have a reason to engage in espionage!
In GalCiv I there really wasn't any reason other than to avoid one of the random events. In games where I was behind espionage was too expensive and in games where I was winning there was no need.
I expect espionage to be vital in GalCiv II:
Thinking of stealing a resource square from the unsuspecting Altarians? With a little espionage you can see what you're up against before commiting to a war.
Have the Drengin started demanding tribute? With a little espionage you will know what weapons tech to research before they inevitably attack.
Would you like to see the Torians go down, but you don't want to bloody your own hands? Give the Korx the weapons tech they will need in exchange for a war declaration.
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It's definately too late to add any features, but I have a suggestion for the expansion pack to GalCiv II -- something I haven't seen in any other 4X game. Currently the diplomacy screen shows all techs researched by the other civilization that my civ does not yet have. I suggest that techs showing in the diplomacy screen have the additional requirement that I have either seen that tech in action or know it exists through espionage. Lets say the Yor have researched Habitat Improvement. and I have not. I should not see that tech in the diplomacy window unless I have invaded one of their planets, have a high enough espionage level with them, or they have chosen to reveal it to me..
Perhaps all my opponent's ships have lasers and I have shields on all of mine. It would be great if they secretly researched missile tech for about 50 years and then suddenly rolled out their next generation missile boats, suddenly turning the war in their favor. if I had been spying on them I would have known that they were researching missiles and possibly have researched missile defence, but as it is I have possibly lost the war.