The emergence of digitalisation and COVID-19 have induced notable lifestyle changes. For example, contactless online-offline engagement remains popular even after the reopening of physical venues. This demand has led organisations to advance their technologies via gamification and improve customer experiences and involvement. Hence, this study examined how retail store cross-boundary alliances and gamified marketing methods impact the implementation of online-merge-offline (OMO) virtual-physical fusion services from customers' viewpoints. An evaluation model was developed by integrating Chou's eight-core Octalysis framework for gamification and decision-making approaches. Furthermore, an online survey performed in Taiwan generated 550 valid responses. The empirical data were subsequently analysed with DEMATEL to determine the interconnections among evaluation indicators and construct an influential network relation map (INRM). The indicators' influence weights were ascertained via DANP. Unpredictability (Unp) was ranked first, followed by avoidance (Avo), epic meaning (Epi), scarcity (Sca), empowerment (Emp), social influence (Soc), ownership (Own), and accomplishment (Acc). Both Acc and Unp were the most and least significant factors, respectively. Optimal gamified marketing approaches positively influenced customers' repurchase intentions, shopping experiences, and retail loyalty. Overall, retail stores seeking to apply cross-boundary alliances and gamified marketing methods can benefit from the empirical outcomes to incorporate efficient OMO virtual-physical fusion services.