If you want to make a highly reflective, but relatively non-shiny texture, then you will have to up the reflection color (blue) in the data texture to the max, while keeping the diffuse color in the color texture completely black. This will give you a sort of "dark mirror" effect.
However, I have to tell you that the game engine does not actually reflect other objects from the reflective surfaces - things like that are very processor intensive and are usually only used for water and such. What the Sins engine does, is reflect the environment sphere which is also used to provide ambient illumination for the ships. So what you will get is pretty much the same if you used a light-grey color and total reflectivity - a sort of metallic mirror effect, only darker.
Cloaking effects, aka the Predator, are achieved by applying a special refraction shader, not reflection, so that the object appears as if made from glass. But this sort of shader does not exist in Sins, so unfortunately we can't use that effect (I'd love to use it for explosion shockwaves, shield hit effects and black hole visualisation...)
