@CA: That's a good point, but I'm not sure if it's what he was meaning.
Let's say that the Arbiter gets a note from the Spy in round three and decides to spring into action immediately. Under Berenzen's idea, the Priest would be able to bring the Arbiter back to life but the Arbiter would be unable to kill another player until round four.
It's an idea, but I think it's worth examining to see if it's still overpowered for the Arbiter to get two kills, even with that restriction.
You are right though. If the Arbiter initially acted in round five before the Spy asked their question, then there would be little reason for the Priest to resurrect them since the Arbiter would have lost the power in round six anyway.