Reconstructing the mandible after the surgical removal of diseased sections is crucial for restoring functions such as chewing, speech, and facial integrity. However, achieving consistent bone union remains a significant challenge. This study hypothesizes that optimizing donor bone cuts, specifically through improved positioning and cut plane orientation, can enhance bone union outcomes. To test this hypothesis, we present a novel automated workflow that leverages Bayesian optimization. Applied to a mandibular body defect case, this approach integrates virtual reconstruction, remeshing, and biomechanical simulation, resulting in up to a 76% increase in predicted bone union propensity. Our findings indicate that donor cut planes warrant greater emphasis in surgical planning. Furthermore, automated optimization underscores the potential of this patient-specific, data-driven method to advance bone healing in mandibular reconstruction.