[sidusar]

Indeed, so the only way to simulate a building being built, would be to place a large pile of rubble on top of the building so that it completely covers the building, then despawn the pile of rubble when the event is triggered.

You can then despawn the building itself later, to simulate it being destroyed again. However, then you're stuck, and only a restart of the scenario will restore the initial situation. A base that indefinitely grows and shrinks dynamically as the situation changes, is not possible.