The idea of using Augmented Reality (AR) user interfaces (UIs) to create 3D media content, such as 3D models for movies and games has been repeatedly suggested over the last decade. Even though the concept is intuitively compelling and recent technological advances have made such an application increasingly feasible, very little progress has been made towards an actual real-world application of AR in professional media production. To this day, no immersive 3D UI has been commonly used by professionals for 3D computer graphics (CG) content creation. In this paper, we are first to publish a requirements analysis for our target application in the professional domain. Based on a survey that we conducted with media professionals, the analysis of professional 3D CG software, and professional training tutorials, we identify these requirements and put them into the context of AR UIs. From these findings, we derive several interaction design principles that aim to address the challenges of real-world application of AR to the production pipeline. We implemented these in our own prototype system while receiving feedback from media professionals. The insights gained in the survey, requirements analysis, and user interface design are relevant for research and development aimed at creating production methods for 3D media production.