have you done any tests to see if dragging around an interior hurts performance? im not sure if this is correct, but i think as long as actors are parented, they should be using a local coordinate system relative to their parent, so moving the parent should not need to update the coordinates of anything attached to it. if attaching actors does cause any performance problems, you could optimize it by using fewer separate parts, combining most of the interior into a single object, and trying to use as few draw calls as possible.
you could make a test actor that spawns a few thousand cubes, attaches them to a parent, and moves the parent around. then you can find out how many objects it takes to actually hurt the frame rate, but it really depends how you want to make your spaceship. i think if you use as few materials as possible, and use instanced meshes and combined as many parts into a single static mesh as you can, it shouldn’t be a performance problem.