A door assembly for a motor vehicle comprised of an outer door panel and an inner door panel interconnected to define a door panel structure having an internal door cavity. A collapsible carrier module is configured to be oriented in a collapsed arrangement to facilitate installation into the door cavity through an opening in the inner door panel. The collapsible carrier module can be moved from its collapsed arrangement into an expanded arrangement upon installation within the door cavity to facilitate subsequent mounting to the door panel structure. The collapsible carrier module includes a two-piece carrier plate formed to integrally include a pair of laterally-spaced glass run channels and a pair of laterally-spaced slider rails.