While you can move ships using the Y axis to put them above planets, you canno place the structures in the same way.
While I was thinking about it the other day and I've come up with a easy way to place objects on the Y with the AI. This examples uses a Gauss cannon Object to be placed near a other vital logistic object.
Known locations that do not change
Location of Planets will always be (0,0,0)(X,Y,Z)
X= Radius Location, North side, West Side, East Side or South, in relation if you were standing on the Earth.
Y= Height of object Compared to Gravity Well
z= Depth of Location, how close to planet/gravity well.
Location of a vital Object, Military Research Station (0,70,50). This puts the object 50 blocks away from the planet, 70 blocks above the gravity well. Currently the player is busy so he doesn't have time to place a guass cannon. Well then lets use some geometry skills. The computer draws a direct line to object and goes through the object stopping 10 blocks after. It places the object in that location, the point after. There we go, we have a guass cannon autoplaced in the right location so the any attackers the come to attack the logistics have to take a longer route around. There is another option to auto-place 2-3 turrents though.
Even more Geometry Skills!
The values have the same location as before. When the computer draws the line to calculate the axis of the line changes to not match the axis/rotation of the gravity well. When this line reaches the logistic object the line stops and three lines branch out from it. First one contains a line the goes at (45,45,0), second (0,45,45) and third (45,0,45). The lines stop at 10 blocks from the point where is branched. What this means is that all of the placed guass cannons will be facing all the outside angles from 3 different locations. Basically imaged a 1/3 of a sphere faced the outside of the gravity well with 3 Guass Cannons.
What this leads to is now the computer AI can use the Y (Height) more often and make game play more interesting. It doesn't necessarily make the game more complex than it has to, as ships already automatically use the Y (Height).
More Geoms!
What happens if the AI wants to place a logistics object behind a military object like a Guass CAnnon? I've thought of a way to add that too. Again the values are the same as before, as the most important value is the gravity well. A line starts from the Guass cannon to the planet, it stops at 10 blocks from the Guass cannon. There is another way to calculate this but my brain hurts...