Space system engineering is a complex activity, spanning multiple phases and involving different stakeholders using a variety of engineering approaches and tools. ESA has been investing in Model-Based System Engineering (MBSE) research for many years, developing different MBSE frameworks and tools. Most of these have been focused on specific engineering phases and domains (ground or space). Recently, a broader need has been recognized across space institutions and industry in Europe to focus the MBSE efforts on semantic interoperability and associated model integration. This has led to the Model Based for System Engineering initiative, aiming to guide the development of a common space systems ontology and an MBSE Hub to support both aspects. In this context, we propose a study for developing an End-to-End Space Systems Engineering Portal. The portal will be a downstream application, offering a federated, web-based User Interface (UI) layer on top of the MBSE Hub infrastructure, where stakeholders will be able to develop own contributions for engineering data exploration and integration in line with the space systems ontology. The portal will enable end users to integrate data, identify data gaps, and transition models between different engineering phases and formats using intuitive techniques on the UI level such as e.g. enterprise mash-ups and visual analytics. On the architecture level, the federated UI layer will utilize advanced techniques such as e.g. micro-frontends, portlets etc., allowing different stakeholders across the space system engineering lifecycle to build their own portal contributions for the MBSE approaches and tools utilized by them, in a controlled manner, using their preferred technology stacks and available skill-sets. Therewith, the envisaged federated UI layer can amplify the results from the MBSE Hub and common space system ontology studies and facilitate the associated MBSE adoption in an ecosystem of empowered, contributing stakeholders.