Ading tactical combat would dramatically change GalCiv, and IMO not for the better. Let me describe how GalCiv is:
You design ships, you arrange fleets, you send your fleets to attack other fleets, then the best part, watching the battle unfold (which could be done in a more dramatic fashion, and I hope this is addressed in GC3).
This is what GC is, and I love it this way. Adding TC, would destroy the battle viewer, and turn GC fleet battles into little more than 'advance wars' for the game boy. This IMO would destroy the joy of watching your fleets do battle with the enemy. That's not to say that tactical combat games aren't great and don't have their place, they do. But it's not what GalCiv is all about.
Perhaps we all need to take a breath and read Brad's wise words in the link below, they're as true today as ever.
"...But Galactic Civilizations has always been a strategic game. It's never been a game about tactics. It's literally a class of civilizations."
Watching the battles unfold with out any imput was the most unsatisfying and frustrating thing about GS2. And I'm not the only one that thought that. I can't remember how many times I've heard or said "This game would be totally great if there was Tactical combat." The frustrating part is that you would design these cool custom ships yet you had no control over them. GS2 was a good game and the only thing it really needed was TC to make it great. You don't have to give up anything else in the game in order to have TC and I don't under stand why some people think this.
Personally if they had TC I would never ...EVER use auto resolved because it is simply boring. See AOW3 or other AOW for an example of good TC. Then add that to the GC good Stratagy Elements and you will have one awsome game. And yes throw in the boring Auto-reolve for those that hate TC.