Neither you nor the AI (ally or enemy) can order stomps to happen, they can only happen due to the ground a unit is standing on ceasing to exist without having an appropriate Fly or Swim movement type. Correct me if I'm wrong, but I don't think you can even use the fog of war to order stomps, because the pathfinding accounts for hidden units too. So the stomp mechanic isn't an actual intended attack, but merely an error handler to prevent two units from occupying the same space. Just KO the unit with the lower Z value
The pathfinding does not account for hidden units.
So, in theory, you can use the fog of war to "order" a stomp... but the likelihood it actually happens in very VERY low:
a/ as you walk the fog of war will likely disappear, unless you make yourself or the enemy vertically tiny (to prevent seeing them from diagonally above)
b/ even if you somehow manage that, there's still 8 neighboring tiles, where the enemy will be pushed before it would be stomped
Another, almost equally hard to do attempt, is to blow up just the floor below a unit and let it fall on another unit (that cannot be forced into any neighboring tile).
But you are correct, stomp "mechanic" is designed only as means of preventing 2 standing units occupying the same tile.
If it happens, enjoy it, you've won a small lottery
As I toy with move types and flying I conclude that current handling of falling is not satisfactory.
I think of adding option for damaging unit when it fall from heights bigger than 1 level, question is how should it be calculated and what it should "damage"?
Another thing is that falling unit always can knock out lower unit, even when its lot bigger and stronger unit, at least 2x2 units should withstand 1x1 unit and small one should be knockout instead.
Any thoughts on this topic?
To be honest, I like it the way it is.
If you want to add more features here, make them optional/configurable please.