A software product line primarily structures the software architecture around the commonalities of a set of products within a specific organization. Commonalities can be implemented in prefabricated components, and product differences are typically treated by well-defined variation points that are actualized later on. Dynamic, domain-specific aspects, such as ad hoc customization by domian experts, are hard to model with static extension techniques. In this paper, we will discuss open issues for dynamic and domain-specific customizations of product line architectures. We will also present an indirection architecture based on Component Wrapper objects and message redirection for dynamically composing and customizing generic components for the use in concrete products. As a case study, we will discuss two designs from a Multimedia Home Platform product line: end-user personalization across different new media platforms and customization of interactive applications by content editors.