I'll be interested to see what you turn up. Energetically that would be the place to do it. How much CO2 could potentially be harvested in those months? What would the energy costs be to solidify it and then maintain it in that form for the rest of the year when ambient temperatures are considerably higher? Even stacking it on the ice to form the CO2 mountain would lead to sublimation due to conduction of heat from below as the Earth's natural heat bleeds up through the ice. The ice itself is warmer than the necessary temperature for keeping the CO2 frozen. Could we ever capture the CO2 with less emissions than needed to do accomplish the feat? There might be a scale of production that reduced surface loss rates enough to be somewhat sustainable through the year, basically make 2 units and save 1 unit by the end of the year. However, at best case, even if the energy trade off can be worked out, we would be creating a growing but very unstable CO2 reserve that would quickly return to the atmosphere if we ever stopped refrigerating the South Pole. One little economic glitch that stops the South Pole resupply and all that work would literally evaporate.