Since war is a huge part of any 4x strategy game, here are some changes to the combat from GalCiv2 that I'd love to see implemented in GalCiv3.
-When I first encounter an alien spacecraft, there's no good reason why I should be able to right-click on it and see its exact weapon and armor specifications. This should require some espionage, advanced scanning technology, or first hand experience fighting the ships. It would make you think twice about declaring war on newly encountered races, and give other races an aura of mystery.
-AFTER you gain the espionage or technology described above, it would be nice if right-clicking would show you the odds for winning an encounter. The AI should also make use these odds when deciding whether or not to attack. In GalCiv 2, a commonly observed AI stupidity was that the computer would waste wave after wave of ships in futile attacks on fully upgraded military starbases, when a much better use of those same ships would be to attack the ships guarding your planets.
-The weapon technologies in GalCiv 2 were a little boring (Laser 1 -> Laser 2 -> Laser 3 ...). I guess it makes sense to have a linear progression in some cases, but could we also have some more unique weapons and defenses?