Background: Shoulder muscle weakness (e.g. in Erb’s palsy) limits the ability to lift the arm and requires high muscular activation to perform and sustain elevation leading to rapid fatigue. This leads to a restricted reachable workspace resulting in impairments in daily activities . Although passive shoulder exoskeletons based on gravity compensation reduce muscle activity in healthy individuals, the effects on muscle activation, shoulder kinematics and activities of daily life under reduced shoulder strength conditions remains unclear. To our knowledge, no orthosis/exoskeleton is currently available for supporting arm elevation through gravity compensation principles during activities of daily life. Methods: This mixed-methods feasibility study evaluated whether passive gravity-compensating shoulder assistance can restore muscle-driven elevation capacity and reduce muscular activation under graded weakness. Additionally, user-informed design requirements were identified using semi-structured interviews exploring daily limitations and needs for support in adults with Erb’s palsy. In parallel, musculoskeletal simulations in OpenSim modelled abduction and forward flexion under strength reductions corresponding to MRC levels 2-4. Outcomes included peak and cumulative muscle activation and the resulting maximal muscle-driven active humerothoracic elevation range of motion. Assistance was implemented using gravity scaling and a physically modelled cam-cable actuator. Results: Interview findings highlighted rapid fatigue, restricted elevation, and reliance on compensatory movement strategies, alongside strong requirements regarding comfort, adjustability and selective use. Simulations showed that weakness reduced maximal muscledriven range of motion. Passive assistance restored full elevation with 15-45% gravitational compensation, depending on severity of weakness, while reducing peak and cumulative activation without disproportionate compensatory activation. Conclusion: Passive shoulder elevation support, implemented through both gravity scaling and a modelled cam-cable actuator, under simulated weakness and aligns with user-identified needs, supporting further orthosis development.