As I understand it, the bridge piece is part of the "base" kit. It's even designed so you can either have the capt's chair, the helm and the viewscreen aligned straight forward, or turned counterclockwise to have the turbolift alcove align with the "cylinder" sternward of the outer bridge dome.
Even the shuttle, as tiny as it will be, is composed of 4 pieces, the main hull, the two nacelles and a piece to form the proper "step-stair" arrangement of the impulse (?) engine. Now that's