I've played many games like this, probably all of them, and a few with tactical battles. I've played games with excellent tactical battles, this being Space Empires 4, and others with very poor battles like in Pax Imperia 2.
I dont think at all that they should use Real Time battles, if they plan on doing this. Its either going to be overly complex, like Homeworld, or its going to be JUST like the battles now. Right click an enemy, watch ships fight, etc. That is how it was in Pax Imperia, the battles are just like it is now except you choose what the ships attack first. It also shouldn't be like on the RTS space games like those Star Trek armada games or the ones simular to it. Right click, ships sit their and shoot until dead. Of course that is exactly like the Pax Imperia (or galciv 2 with right clicking) style except the ships dont move.
The combat needs something MORE for tactical battles. I'm not saying dont do RTS battles, it can be done right in a easy and quick way that is actually good. I think Empire at War gets close to it if the game were refined people would think more highly of it. Though I personally think the battles in GC2 should resemble more is a much more refined Nexus if they want to do RTS.
I personally would obviously like Turn Based battles. The game whose battles I enjoyed the most was Space Empires 4. Lots of ships with a huge variety of special abilities, various ship classes, large battles, lots of types of guns that do different things. If you take Galciv 2 the way it is now the battles would be incredibly boring. All ships being exactly the same, pretty much, all guns being the same besides doing different damage, no special abilities, etc.
It will need a lot more work then just adding battles otherwise its a waste of time.
I personally think that refining ground combat is something that needs more attention than tactical battles. I'm sure if that were put up on the list it would be been #1.