Maybe stupid, but it's my idea for event.
"Gecko's siege"
Background: The First Citizen of the Vault City and VC military leaders, known from thier antipathy to Ghouls wants to resolve the problem with damaged Nuclear Power Plant in Gecko by killing the Ghoul leaders (without them, other ghouls may have a serious problem because two most skilled technicians are in the leading council) and shut down the reactor. One man, who spying for Gecko has informed Harold about VC's plans. He decided to form and lead the Gecko Defence Forces. The both sides needs a manpower...
Rules: Slpit players to two teams.
1. Vault City Strike Team: the primary goal is to kill Ghoul leaders (placed around Gecko and heavily guarded). Secondary objective is to reach the reactor core (also heavily guarded) and shut it down.
2. Defenders of Gecko: thier objective is to kill all enemy. Bonus objective: Kill the VC First Citizen who've decided to lead the assault herself.