Accurate calibration of in-plane plastic anisotropy is essential for reliable numerical simulation of sheet metal forming. Conventional identification procedures rely on combining multiple standardised tests, such as uniaxial tension along different material directions and equibiaxial loading, each probing only a limited subset of the material response. This work revisits the long-standing question of whether the full in-plane anisotropy of sheet metals can be characterised using a single, well-designed experiment. A purpose-designed heterogeneous biaxial tensile test employing a cruciform specimen is proposed. The geometry is tailored to simultaneously activate predominantly uniaxial stress states aligned with the rolling, transverse and diagonal directions, while maintaining low strain gradients suitable for accurate digital image correlation (DIC). The specimen is deliberately conceived as a well-defined test configuration for full-field inverse identification, with known locations and loading stages at which relevant material information is embedded. The identification strategy is formulated within a Finite Element Model Updating (FEMU) framework and applied to the YLD2000-2d anisotropic yield function. Two parameterisations are investigated: the classical formulation based on abstract model coefficients and an alternative formulation expressed in terms of physically interpretable quantities, namely uniaxial yield stresses and R-values. Sensitivity and identifiability analyses demonstrate that the physically based formulation significantly improves the conditioning of the inverse problem and enables unique identification of all parameters from a single full-field dataset. Virtual experimentation confirms the robustness and accuracy of the proposed “one-test” strategy, even in the presence of modelling and discretisation discrepancies. The results demonstrate the potential of the proposed configuration to support systematic validation of full-field inverse identification methods and to advance practical implementation of Material Testing 2.0 in sheet metal characterisation.