[VelRa]

What I would like to know is how they are manned/defended and how are they destroyed.

My vision of attacking one would be as follows: four stealthers enter the ship from four different access points, remaining undetected and scouting the current defenses as well as the loadout. They plant a virus which reduces the effectiveness of the ship's hardpoints and make their way to a shield core where the shields are powered. While the enemy is distracted defending the shield core, two galaxies land on the two airpads on each side of the ship, and the full-scale attack begins. Both teams bring in air vehicles to defend, while in the battle below AA focuses on several weak spots in the air cruiser's defense. The cruiser is destroyed if either its hull suffers too much damage or its internal drive core is destroyed.

And to defend, it would look something like this: A vigilant crew mans the hardpoints and participates in the air battle nearby. It spots incoming stealthers and moves quickly to shut them down. A warning is sent out, and people know to spawn in the cruiser to defend. When the Galaxies arrive, they are overwhelmed.

It might look something like this or somewhere in between the two.