The extension of infrared interferometry to an array with a large number of telescopes and kilometric baselines such as the Planet Formation Imager represents an exciting but formidable challenge. Such an infrastructure will require major technological developments, with several key aspects still to be solved on a mid and long term horizon. Mid-infrared heterodyne interferometry is considered as one potential technology despite its well documented lower sensitivity but its stronger scalability and lower hard infrastructure requirements. Exploring pathfinder instruments is a way to increase the maturity of interferometric technologies. In this study we propose to use the 8 VLTI telescopes (Unit and Auxiliary) as a coherent array using infrared heterodyne interferometry by exploiting the potential of state of the art technology in the field of high bandwidth detectors, laser frequency combs, fiber links and innovative photonics correlator. We analyze the sensitivity of an eight beam combining heterodyne instrument called V8 and present a possible sub-system breakdown. By comparing its performances with the ones advertised by ESO for MATISSE we conclude that V8, despite its lower sensitivity, has an interesting science potential since it allows to trade a higher limiting magnitude with an incomparable better mapping capability. As such it should be a formidable tool to explore evolved stars complex mass-loss processes. Moreover, it should allow the interferometry community to explore pathways for future long-baseline arrays, combining or not, direct and heterodyne interferometry.
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