Having matured over a few decades, the IACT technique is now ready to widen its energy domain as well as to increase sensitivity in its core region (0.1–50 TeV) by as much as one order of magnitude as compared to existing facilities. This will allow to use γ astronomy to search for dark matter, probe intergalactic space and quantum gravity as well as to make efficient observations of extended sources. <br><br> The design of a new-generation IACT array is motivated by the key science questions to be addressed and constrained by the cost of the experiment. A number of performance characteristics impact the scientific capabilities, not just point-source sensitivity, but also field-of-view, angular resolution, energy threshold and others, and the optimization of the parameters at fixed cost defines the approach to simulation studies. <br><br> In this paper, I will highlight IACT array design studies carried through to optimize the array configuration, optical and mechanical designs as well as possible designs for telescope cameras.