Would it be possible to define a tileset width as well? Air units would raise their height if they are over the square that the object was on. However if the tileset object was wide as well air units would return to ground level the next square over. This would be an issue for mountain objects. Glest mountains have a diameter of 3 the mountains i created are 5 in diameter. Units would fly through the mountain till they reach the center where they pop up for a second and fall back into the mountain (cause they passed center square) This would be avoided if you could use either a cell map for tileset or a width property.
Just and idea.