Basically I have an idea:
A kill on sight list in-game. You type in the names of your KoS list in a text bit, and separate them with a comma or to the next line:
*Name1*,*Name2* or:
*Name1*
*Name2*

And upon seeing those names as you're passing them or something, the characters namebar for the KoS person will be a different colour than red, say purple or blue, that way you know they're on your KoS list and can easily kill them rather than consulting your KoS list notepad, or something of the sort.

I have no idea how to make this or any addons, but if anyone wants to take this up go ahead, it's a great idea that I'm sure many other people have thought about. And if you're like me, you're loosing track of people you need to kill on sight.

Something like that for friendlies would be great as well, say they are in green, setable by name or alliance, as the KoS list should be as well.

I've not played it but I hear that Eve has a similar system to this that works very well (despite complaints that you cannot put enough peopl;e in the lists).

As it was in SWG or something like that? That would certainlly be helpful indeed. Or maybe have a color for clans of which you are in war with or something. Nice idea