Amazing thread Tac! Lots of effort put in to it. I would be more inclined to agree with Shooter's theory though. Here's why
1. The tornado seen in the loading screen could be happening due to activity in the poles. Lots of mysterious things happen around the poles. Northern Lights, meteor showers and even solar flares have been documented in the poles
2. In Admiral Byrd's diary, he expresses his shock when suddenly the snow disappears and he is surrounded by flora. He also documents a rise in temperature. It is almost like he discovers a world within a world. We aren't aware of Shangri-La being in the Arctic because we see a hot area full of trees, waterfalls and ancient tombs, which ties in with the Admiral's theory that the Arctic's characteristics just disappeared the further he went on his journey
3. The zombies found in Shangri-La do not look like other zombies. They have symbols tattooed all over there bodies. They are more decayed and diseased looking than previous zombies we've encountered. This could possibly be the Vril-Ya we are fighting. They are an ancient civilization, therefore their bodies have had more time to decay. Also, with time travel tied into the story of the map, maybe we are further into the future where the bodies have had even more time to decay.
4. The 115 rocks found in Shangri-La could mean 2 things. This rock is associated with the Vril-ya and it may not be as extraterrestrial as we think. It may be native to this ancient land. In high concentrations this rock could possibly cause complications with machinery which is why the place is powered by hydro power and not electricity as seen in previous maps. This is also further shown when Admiral Byrd's aircraft shuts down.
Or, the Arctic's position on the poles could mean it is susceptible to meteor showers. Due to the area being in secrecy the inhabitants probably hid the rock underground to mine it. This could also be why the zombies are covered in boils as the exposure to the radiation from the rock could be cancerous.
This is just my 2 cents on the theory. Great thread Tac!