The integration of renewable energy sources within the built environment is a compelling challenge to tackle. With the recent climate targets aiming at a carbon neutral energy supply by the mid-century, a modern building energy system (BES) should maximize the use of sustainable energy resources while coping with the technical constraints of the network infrastructure in balancing seasonal demand and intermittent generation. In order to overcome the latter limitations, traditional BES sizing and scheduling methods need to shift from a building-oriented towards a district-oriented approach to fully benefit from local resources as well as from potential energy service synergies between different types of final users. In view of the current context, this paper proposes a novel method for the integration of sustainable multi-energy systems in different district types of Switzerland. Based on a robust MILP modelling framework, the method consists of two distinct steps: in the first phase, the optimal BES sizing and scheduling problem is solved systematically, generating a set of different BES options for each building type located within the studied district. In the second phase, the final BES configuration is selected among the generated options considering potential synergies within the district. At this stage, local resources such as woody and wet biomass, multi-energy technologies such as power-to-gas and seasonal storage, as well as heating and cooling networks are included in the problem formulation. The proposed method is validated on hands of different case studies: a rural, suburban and urban district configuration. Preliminary results prove that the implementation of a district-oriented method allows for a significant decrease in system costs in comparison to a building-oriented approach while granting equivalent environmental performances. Moreover, the results highlight the potential of district scale multi-energy systems in reaching climatic targets as well as the future role of network operators.