Designing the Community Infrastructure for ESO's Next Transformational Facility. Equitable Governance and Sustainable Teams for 2040s Astronomy

The scientific ambitions of the 2040s will require large, interdisciplinary teams operating across continents, institutions, and increasingly heterogeneous political and funding landscapes. While significant effort is devoted to advancing the technical capabilities of future astronomical facilities, frameworks for coordinating and sustaining the associated community systems are often developed in parallel rather than embedded as coherent, long-term structures at the scale needed to fully realise this ambition. In this white paper, submitted as part of the ESO Expanding Horizons initiative, we draw on experience from established observatories and emerging collaborations to identify key community-level challenges. We argue that a central and transversal scientific challenge for the 2040s is to operate a flagship observatory in which access to telescope time, data, leadership, training, and career development is equitable across institutions, member states, and beyond. We propose that access and participation be treated as integral design parameters, embedded from the conceptual stage and sustained throughout the facility lifecycle, in order to ensure long-term scientific excellence, sustainability, and societal return.