The integration of structural analysis into the conceptual design phase is essential for achieving efficient and sustainable lightweight structures. This work presents a unified CAD-integrated parametric workflow for the design and analysis of thin shell structures using Isogeometric B-Rep Analysis (IBRA). Unlike traditional approaches that rely on polygonal meshes, IBRA enables nonlinear finite element analysis directly on trimmed multipatch NURBS-based CAD models, preserving geometric continuity throughout the process. The proposed framework, implemented via the Kiwi!3D plugin in Grasshopper/Rhino, supports iterative formfinding, performance evaluation, and optimization within the same parametric environment. Through case studies inspired by historical shells, we demonstrate how CAD-integrated analysis facilitates rapid exploration of geometric variations, refinement strategies, and structurally informed design decisions. Results highlight the advantages of seamless geometry-analysis coupling for conceptual design, including the ability to generate numerical hanging models and assess equilibrium shapes under prescribed loads. This approach promotes a shift from “form making” to “formfinding,” enabling performance-driven design iterations and paving the way toward structural digital twins for future applications in lightweight architecture.