Upgrade Call Large Scale Alliance Missions

I think it would be cool, if when creating a large scale alliance mission, there should be an option to 'upgrade' the call. For example, it could start as an explosion then turn to a Aeroplane crash, that now requires more units? Just like a normal call where burning grass can turn into field fire or whatever, but allow the creator of the mission to pick and choose?

So there could be a trigger, such as when a unit rolls up it could change to the upgraded call or after a certain amount of time, so high rise fire, after a certain amount of time could become a collapsed building (Even if all units for the high rise fire have arrived), depending on what the creator of the large scale mission wants to do.