The TeV gamma ray sky is observable by recording footprints of extensive air showers with an array of particle detectors. In the northern hemisphere there are currently two projects employing this technique: The HAWC gamma ray observatory which is currently operational in Mexico and LHAASO in the Sichuan region in China which is currently under development. In the southern hemisphere several efforts are currently ongoing to investigate the feasibility of a similar observatory at very high altitude sites in the Andes. The science case for such an observatory should be complementary to the science to be performed by the future Cherenkov Telescope Array. There are two clear directions in which such an observatory could optimize its performance. Firstly, optimize the performance of sub-TeV energies. This is especially important to provide an unbiased monitoring of a large fraction of the sky for observations of transient and extended sources. Secondly, to obtain the largest photon statistics above roughly 50 TeV, which requires a large collection area with sufficient performance in angular and energy resolution. This would enable to extend spectral measurements of Galactic sources and gives the opportunity to search for dark matter and exotic physics in a new energy range.
Using simulated air showers and a generalized detector description the performance of a conceptual observatory is studied and the ways to optimize it will be discussed. With this approach the baseline design of such an observatory can be obtained without the need of detailed simulations of the detector hardware.