Blockchain is reshaping how agreements are formed, executed, and enforced, yet plural family-law systems in multi-ethnic states pose unique challenges for legal certainty and access to justice. Using a comparative, multidisciplinary design, this study links legal pluralism in family law with the operational realities of smart-contract platforms. We develop and operationalize five instruments—Legal Compatibility Index (LCI), Smart Contract Operational Robustness Metric (SCORM), Regulatory Readiness Surface (RRS), Fuzzy Composite Literacy Index (FCLI), and Hybrid Arbitration Efficacy Index (HAEI)—and apply them across ten jurisdictions and leading blockchain networks. The results show that jurisdictions with proactive legal modernization and judicial responsiveness (e.g., Singapore, USA) exhibit higher compatibility and clearer enforcement paths, whereas formalist or fragmented systems face interpretive uncertainty and remedial gaps. Technically, platforms with high execution reliability and audit transparency are better suited for legal-grade deployment. Hybrid arbitration models that combine institutional enforceability with code-aware workflows outperform purely decentralized or strictly traditional designs. These findings imply that successful harmonization requires coordinated statutory reform, interpretive convergence, sandboxed experimentation, and targeted legal-tech literacy. The paper contributes a replicable framework to evaluate readiness and to guide policy makers, judges, and developers in integrating smart-contract logic into plural family-law environments while safeguarding rights and coherence.