The rapid expansion of renewable energy, particularly offshore wind power in Europe, is set to reshape the continent's power system, transitioning from a rotational mass-based inertia backbone to IBR entities. This inevitable shift highlights the critical need for sophisticated system stability analysis incorporating simulation models from manufacturers to facilitate such studies effectively, that in turn invokes the need for standardizing the interface of simulation models across manufacturers to address compatibility problems associated with the use of different compiler versions and software architecture, confidentiality problems, as well as accuracy and reliability issues in grid interconnection studies, which becomes even more crucial in complex multi-vendor environments. These projects demand simulation frameworks that can seamlessly integrate diverse components while maintaining accuracy and scalability, addressing challenges such as system stability, fault handling, and performance optimization. On the subject of simulation, the effective and less expensive solution for majority of the interaction studies remains so-called offline simulation (such as PSCAD, DIgSILENT PowerFactory, EMTP). In addition, the need for real-time simulations based on replicas to is key to obtain more realistic test results, embedding the out of sight stochastic dynamics introduced by control and communication systems. In this paper, we first highlight the trend towards multi-vendor energy projects, the resulting complexities and issues, and the required adaptation for stability analysis with offline and real-time simulations. This work underscores the need for high-quality models and explores the challenges with the evolving transition and requirements from three vertices of manufacturer, grid operator and test laboratory. We explore the pressing need for multi-vendor simulations, with a focus on offshore wind power. We elaborate on OEM experience with implementation of one simulation tool independent interface, model usage by test laboratory and grid operator to derive key lessons learned from both the challenges encountered, and the innovative solutions adopted. The collaboration between OEM, test laboratory and grid operator illustrate how standardized model interfaces can reduce project timelines and improve the quality of interconnection studies.