Let me try and explain better:
Kill On Sight means that if you see that person you are required/obligated to kill them. So for instance in DarkRP if an admin sets me to KOS, then any player who sees me has the green light to kill me. It is not a slay, but rather 'placing a hit' on someone and allowing other players to kill them.
Even though this COULD be used on multiple gamemodes, this doesn't have any use in an administration mod. I can't speak for the official Ulysses team, but I am quite sure this will never be officially added. You would have better luck coding one yourself or going to the dev corner forum and seeing if someone is willing to make you a small module.