When I go with capital ships, I go with ships that are utilarian. Not space robots. God, I hate the term mecha- I love mechs, I see them as realistic sophisticated machines with guns, rockets, or missiles in reasonable quantity. I see mecha as giant multicolored human-bots that like beating the shit out of everything with metal fists. 

If someone can make a giant metal fist that holds together on impact to something else steel, then I want to use that fist as armor.