Sounds like Angel Arena all over again..
I think he meant 2 teams of 3 players..
Just use a timer, when the timer expires, pause all units, move the top 2 killers to the "arena spot" then use game messages with waits for the 3, 2, 1, go stuff.. really simple.. don't forget to unpause the dueling units after the 3, 2, 1 stuff..