The Horizon Europe project ISIDORe is dedicated to pandemic preparedness and responsiveness research. It brings together 17 Research Infrastructures (RIs) and networks to provide a broad range of services to infectious disease researchers. An efficient and structured treatment of data is central to ISIDORe's aim to furnish seamless access to its multidisciplinary catalogue of services, and to ensure that users' results are treated FAIRly. ISIDORe therefore requires a data management plan (DMP) covering both access management and research outputs, applicable over a broad range of disciplines, and compatible with the constraints and existing practices of its diverse partners. In this poster, as an overview of a peer reviewed paper, we describe how, to achieve that aim, we undertook an iterative, step-by-step, process to build a community-approved living document, identifying good practices and processes, on the basis of use cases, presented as proof of concepts. International fora such as the RDA and EOSC, and primarily the BY-COVID project, furnished registries, tools and online data platforms, as well as standards, and the support of data scientists. Together, these elements provide a path for building an umbrella, FAIR-compliant DMP, aligned as fully as possible with FAIR principles, which could also be applied as a framework for data management harmonisation in other large-scale, challenge-driven projects. Finally, we discuss how data management and reuse can be further improved through the use of knowledge models when writing DMPs and, how, in the future, the contribution of an inter RIs data steward network, to produce a Community of Practice that could be integrated into planned trans-RI competence centres. We propose as a take home message how we will work in this inter RIs network, reusing outcomes from Research Data Alliance, on a multidisciplinary minimal requirement for metadata to enhance inter RIs FAIR data sharing for pandemic preparedness.