As electric bus development shifts toward embedding batteries directly within the chassis, designers face increasingly complex constraints regarding spatial layout and structural stiffness. This study addresses the challenge of optimising battery and structural distribution by proposing a rapid, automated design workflow. This workflow streamlines the process from conceptual layout to a manufacturable detailed design, ensuring a reliable structural framework during the critical early stages of development. The novelty of this research lies in its hierarchical optimisation strategy, which integrates ground structure method [1] with surrogate model. The process begins by identifying critical load paths using the element density method and a ground structure (refined) approach. Subsequently, the workflow optimises node positions and one-dimensional ground structure dimensions within these identified regions. To overcome the high computational cost usually associated with geometric node optimisation, a surrogate model is implemented, significantly accelerating the convergence of the design. This leads to the construction of a 2D ground structure that allows for final refinement into a manufacturable configuration. The significance of this workflow is demonstrated through its application to an electric bus mid-frame. By integrating custom scripts with the Altair software suite (including HyperMesh and HyperStudy), a fully optimised detailed design was achieved within a six-hour runtime. The resulting structure satisfies all original load cases and design requirements while achieving an 8% weight reduction compared to the baseline design. This workflow provides a robust, time-efficient solution for the early-stage design of battery-embedded vehicle structures, offering both computational efficiency and high-fidelity results.