Design space exploration involves identifying a set of design decisions, and evaluating their potential impact on various qualities of a system, such functionality, performance, reliability, and security. This activity is widespread in other engineering disciplines, but is rarely articulated or performed during software construction, despite its potential influence on the security of the resulting system. In this paper, we argue that design space exploration should be an essential part of any secure development process. We outline the key elements of a framework intended to support this activity, and discuss the potential benefits and challenges associated with building such a framework.