So I was thinking of this event for quite a while.
Everyone but 2 or 3 people get chameleon projectors, and hide around the station. The 2 or 3 people without a projector get teleported to the admin test arena (or CC) so they don't see people hide. They get something that deals a lot of damage, but doesn't insta kill people. The goal is to kill every hider.
The only rule for hiders is that they can't leave the station. (No hiding on the outside of the station either.)
The one thing admins have to do is spread the chameleon projectors and maybe set the SMES on unlimited power. Maybe a preset can be made to give chameleon projectors automatically.
A variation can be done where instead the seekers are zombies, and hiders of course get infected when they get caught, the classic infection mode.