There is a need for lighter, more agile technology that can be easily updated to remain relevant and deployed where and when the Warfighter needs it at a lower cost to supplement high fidelity simulator training. This is where virtual, augmented, and mixed reality (extended reality, or XR, collectively) technology comes into play. While individual XR training applications have great potential, an ecosystem that synergistically deploys complementary applications has potential to truly explore the full benefits of XR training using modular open systems approach (MOSA). A Lightweight Simulator Ecosystem (LSE), made up of complimentary training technologies, built with a MOSA, and equipped with connections to complementary applications, provides a place for agile and responsive training to flourish.  The complementary technologies include both user facing applications (i.e., XR training games, interactive models, virtually instructed lessons, quizzes, and exams) and the components that make these applications (i.e., 3D models, photogrammetry, terrain maps, Artificial Intelligence/Machine Learning (AI/ML) models, assessment & visualization tools). The connectivity to related applications can be to Learning Management Systems (LMS), Learning Record Store (LRS) and other external systems for secure and reliable data exchange. Building and operating a MOSA LSE is no easy task; it requires collaboration and shared development practices among entities while operating in a multi-vendor, multi-organization military environment, with the desire for continuous delivery of training across the enterprise in an accredited, secured cloud platform. This challenge requires a cooperative development space, similar to the successful open-source development, a ubiquitous marketplace for delivery to users, much like the mobile App Stores, and robust compatibility of multi-vendor hardware and software. This paper will discuss how these challenges are being addressed for implementation in the future LSE for the Air Force Life Cycle Management Center’s Simulators Division.