This idea springs from the vendor killing problem, but kind of expanded into a new kind of missions as well.
We all know some attack vendors for sport, and many of us would like to help the vendors, as they apparently have no communications and cannot call the guards...
Mission Type #1
Lets say a vendor is under attack. If you wish, you can then offer your help, allowing you to assist him/her/it against the assailant.
This could generate a mission of the assassination type with the assailant as the target.
I dont think any rewards should be given, at least not a big one, maybe a symbolic nodrop reward, one unique version for each faction. If money or valuable items were given, people would exploit it.
Being allowed to help should be the main purpose.
Mission Type #2
Bodyguard / escort missions in the open.
get an escort mission, and an NPC of your alignment spawns, following you to the mission area. If the NPC makes it, you get your reward. I'd suggest having the NPC linked to you in the same way as a pet, in that noone can attack it unless they are allowed to attack you. Thus stopping random players from killing it outside PvP areas. The NPC might take orders like wait and follow, but should not be able to attack anything, maybe allowed to defend itself under attack.
This would be an interesting addition I think. Something to do for those who are fed up with dungeons