Yeah, killing randomly any regular staff from your master is one way ticket to death :P. Even as Leonidas I did not go that far; injury of staff member (a non-hindering non-permament kind injury) would result punishment somekind. Actually killing important NPC would result a very gruesome death. Reason why any acts of mutiny or disobedience is heavily punished is meant discourage said actions. As if lanista does not punish gladiators going off the line, it would encourage other gladiators learn bad habbits.