Initiate battle over cliffs with range units

Situation

When I found a good choke point on the map which I want to defend with units, I always founded it strange that the only way to block it is to stand on the low ground in the middle of the choke point. This method makes defending battles almost equal on both sides, based on the limited option of the starting tiles of the tactical map due to the surrounding cliffs or mountains.

My first thought in this situation was then why not just build a garrison on top of a cliff next to the passage or put a watching/defending army there. This method only gives ZoC to the tiles, which slows down the enemy armies. But there's no way to initiate an attack from the cliff to fully stop them.

Solution/Idea

If a "Ranged" unit (maybe "Gunner" as well) is part of the defending army, the army gains an extra ability similar to a Bombard action on the Siege Artillery unit. This ability should have two options based on the situation.

a) If the army, which passing through is capable of reaching the defenders on the generated tactical map, then this action would only initiate the battle. In this case, the only change would be that the battle was started through a cliff and not by a melee attack as it used to.

b) If the terrain is impassable between the two armies then it will lunch a single strike for each "Ranged" unit in the defending army. The damage would be calculated similarly to the bombard ability, just this one is a single tile ranged and can be only lunched against units/armies.

Conclusion

Width this new unit action, defending or attacking choke points wouldn't feel strange, at least for me. But might be some of the combat modifiers need to be adjusted to it, like high ground.

This is a vague idea, but I would love to hear some thoughts on it from other players as well.