This looks really good. Nice to see someone not being afraid of making asymmetrical maps.
It is very hard to combat that the gameplay defaults towards turtling though, and as bigger the map, as harder it becomes. But many people like this gameplay too. What kind of gameplay do you want to have with this map?
Avoid placing too much reclaim, it creates only work to reclaim it, and there is enough work to do on big maps. Low mass reclaim for deco is okay, but if you want high mass reclaim, make only 1-3 spots, and not too much of it (like 2000 in center i.e.)
The two players with 8 mex at start position should rather have 6, and move 2 more towards the center and make them contestable by both teams. Unless you want the map to go to t3 stage faster (but there will be already almost no t1 and t2 stage, mostly due to size, you can combat this, but it is not easy)
If you can, do something with props/decals/textures to make it easily visible where there are passages in the mountains.