Please help me with the following idea.
I would like modify how alien retaliation works in my mod. Instead of one behaviour (base assault), there would be two missions, chosen at random according to weights:
* mission 1: standard base assault
* mission 2: an "air domination" mission, where many hunter-killer UFOs are spawned to patrol the affected area and get in the way of X-Com operations for a while.
Making the missions themselves is trivial (one is the vanilla retal, the other a generic mission with UFOs), but how do I script it?