Parcel delivery volumes are increasing all over the world and come with an increasingly large footprint in emissions and energy consumption. We describe a replicable modelling pipeline for last-mile parcel deliveries in which all operators of a region are represented as cost minimization problems that are sensitive to the spatial context, vehicle types, and cost structures. For the use case of the Metropolitan region of Lyon, a future scenario for 2030 is faced with various policy interventions. The results suggest that emission levels of 2024 can be maintained by implementing a purchase tax on internal combustion vehicles of more than 50% or a carbon tax of more than 750 EUR/tCO2eq. Full electrification yields an emission reduction compared to 2024 of 80%. All proposed policy scenarios show lower per-parcel costs compared to 2024 due to scaling effects of increasing parcel demand and density.