Mixed ionic–electronic conductors (MIECs) are promising materials for next-generation electrochemical systems because they can simultaneously provide ionic and electronic transport, thereby mitigating limitations of conventional solid electrolytes and cathodes. To systematically discover such materials, we developed a structure-guided multi-stage screening framework applied to sulfide A–M–S compounds collected from the Materials Project. Starting from 442 candidates, sequential filters were applied: compositional and physical criteria, transition-metal polyhedral normality, A-site percolation connectivity and hop-distance fitness, and thermodynamic stability (Ehull ≤ 0.15 eV/atom). Redundancy removal yielded 13 prototype frameworks that satisfy both ionic and electronic transport prerequisites while retaining synthesizability. Scoring across five criteria further prioritized candidates for experimental validation. This work establishes a generalized, structure-based methodology that moves beyond simple energy or band-gap descriptors, offering a scalable foundation for designing doped and defect-engineered MIECs. The framework is expected to accelerate development of cathode and electrolyte-additive materials for all-solid-state batteries.