This paper presents a comprehensive approach to designing hybrid integration frameworks that bridge SAP Revenue Growth Management (RGM) and SAP S/4HANA platforms, emphasizing sustainable development principles. As enterprises increasingly adopt digital transformation strategies, seamless integration between legacy and next-generation ERP systems is critical for operational efficiency and business agility. The proposed framework leverages a combination of on-premises and cloud-based middleware solutions to enable robust, scalable, and maintainable data and process integration. A detailed real-world case study demonstrates the practical implementation, highlighting challenges, architectural decisions, and performance outcomes. Sustainability is embedded through modular design, resource optimization, and lifecycle management practices that reduce technical debt and enhance long-term maintainability. The study concludes with insights into best practices and future directions for integrating complex enterprise systems sustainably.