Note that this requirement gives a VERY big restriction on the last wave since the only ways to do this would be with a tank or lots of filter work. The tank has an on destroy which you can use as trigger if the tank spawns when everything is dead The bots can be detected with a trigger and filter which must cover the whole map and basicly behaves inefficient. You normaly wouldnt tag the main bots. It gives a huge room of error. Not to mention it breaking the whole idea of what MvM currently is about: its about defending. Otherwise you should be in the blue team. And there is no MvM map capable of doing that without a mod. And as a last question, how would you bring focus to that ship? If you put it at a logical place it would be at the bot spawn. A place you often wont see at certain parts of the map since you get pushed back (if not, your wave is too easy as last wave or you play on a too easy mission). So if you win the whole cinematic event can simply be missed. Not to mention it not making sense to randomly blow up (although, the rambo movies have similar events). To me defending the mothership is much better out of MvM logic and also easier to make. EDIT: For that matter i do suggest an alternative. Allow that mothershop to attack the red base for mvm to destroy something there. This at least gives the feeling of being attacked by aliens.