The easiest way to see if what you want will work for a civvie design is to check the box just under the components screen that says civie only. Things that will not make a ship military are: Size one sensors both actives and passives are fine, armour (needed for nebula systems) ciws, military jump engines, civilain jump engines, troop transport bays, civilian engines, sorium harvesters, terraforming modules. There are probably others but I don't have aurora on this machine.
Brian