First I must say I have absolutely no idea how developers want to implement karma.

But thing about bonus from karma and ani-pk. My suggestion is that you take a perk "bounty-hunter" (something like slaver). Then you can see which bounty is possible to collect (pk name + price on his/her head). After you kill this pk you loot a "dog tag" from him and bring it to bounty hunter's office.
Maybe also add a name colorizing or something to distinguish bounty hunter's target.
How to increase a bounty on your head? You need a negative karma and you must kill someone with karma > -100(?). After you do this bounty on your head will increase by 5-10 caps (I hope this ammount won't be farmable - not worth dying). After someone collect bounty on your head it will drop back to 0 and you can increase bounty on your head once again.
Please don't argue that if you shoot someone in desert there is no one who can report the crime. Because that is realy poor argument.
I hope this suggestion make any sence. This may be a chance for those who just don't want to shoot everyone on sight.
I think something like this is working with Hub police but I am not exactly sure how.