End-user redesign has been coined as a phenomenon that may happen within IT platforms such as Facebook or Wikipedia. However, redesign or secondary design outside the boundaries of a platform is under-researched. Existing prescriptive knowledge is limited to designing functionality of an artefact with specific boundaries where redesign can take place, not on why and how to enable novel unbounded redesign outside the original scope that can benefit decision making and organisation. Hence, we need design theories that can help primary designers create artefacts that allow unbounded secondary (re-)design. We propose design principles for this unbounded secondary design. The principles are derived from a group decision support tool case that was presented, redesigned and infused into two different organisational domains. Thus, the contribution of the paper is a design theory in the form of two times three design principles aimed at supporting the secondary design process and the form and function of the secondary design.