This paper describes a method for the early stages of new product development that supports the conceptual design of modular, platform-based, and customizable components. The method includes up-front product planning encompassing definition of customer requirements, market segmentation, and competitive product analysis, ultimately leading to product specifications. The results from product planning are combined with tools for developing a product platform architecture with easily customizable customer interface components, which are based on well-defined interfaces. The method and tools are applied to a family of bactericidal door handle products. The major elements of the customizable door handle product architecture are defined, and several concepts are generated that utilize modularity, customization, and product platforms within a single design. The results are discussed in detail with specific comments on applying up-front planning and design tools in terms of modularity and customization for commercialization based on well-defined interfaces. Finally, we conclude with comments on the limitations of the method, proposed improvements, and future work.