Regarding the upgraded Kashchei, I think it's unfair - it's better to make a percentage-based link to the damage. Otherwise, it's very cool at the beginning of the game, but it becomes irrelevant towards the end of the map when the damage is already measured in thousands. And it could also be politically conscious and change the Knight and Bear? I had a similar idea myself. You could incorporate a chimney into the hut on chicken legs, like the Necropolis. And draw the Mage Guild as the Spasskaya Tower with clocks. The Castle could be in the form of the Kremlin.