Software process models need to be variant-rich, in the sense that they should be systematically customizable to specific project goals and project environments. It is currently very difficult to model Variant-Rich Process (VRP) because variability mechanisms are largely missing in modern process modeling languages. Variability mechanisms from other domains, such as programming languages, might be suitable for the representation of variability and could be adapted to the modeling of software processes. Mechanisms from Software Product Line Engineering (SPLE) and concepts from Aspect- Oriented Software Engineering (AOSE) show particular promise when modeling variability. This paper presents an approach that integrates variability concepts from SPLE and AOSE in the design of a VRP approach for the systematic support of tailoring in software processes. This approach has also been implemented in SPEM, resulting in the vSPEM notation. It has been used in a pilot application, which indicates that our approach based on AOSE can make process tailoring easier and more productive.