Mergers and acquisitions (M&A) are strategic maneuvers that have long been intertwined with the hospitality sector, involving the asset consolidation among hotel groups through various partnerships. While extensive research has focused on applying data envelopment analysis (DEA) to assess hotel efficiency, the application of DEA to hotel M&A has been largely overlooked. In this paper, we introduce an inverse DEA (IDEA)-based methodology to evaluate optimal gains from pairwise consolidations among hotels. This approach effectively identifies all productive post-merger hotels, i.e., those mergers with substantial potential for generating resource gains. The relevance of our proposed methodology is demonstrated through a case study of 58 hotels in the Sultanate of Oman. A particularly striking finding is that some productive post-merger combinations implicate only strongly efficient hotels. Individually, these hotels do not require savings, yet when merged, they exhibit significant savings potential, demonstrating that sustainable resource management can be achieved through strategic consolidations. Specifically, our results show that potential post-merger gains can reach 82.81% in bed capacity, 82.44% in room count, 87.91% in workforce size, and 86.75% in employee salaries. These figures are over four times the savings required for individual inefficient hotels. These insights underscore the potential of mergers not only within hospitality but across various resource-intensive industries to drive sustainable development by enhancing operational efficiency, reducing resource consumption, and informing policy that supports sustainable practices through strategic partnerships.