@karstark
Ill comment on disadvantages of assassination and prisoners.
Assassination
As both of us said, game isnt (yet) designed to handle assassination "properly" (stat loss and nothing else for the target). Loot that you get from the victim is nothing else than being a sociopath thief. Assassination is not about stealing stuff, its about crippling or even disabling some organization (be it a small one like a party or a big one like an entire state, or be it just an influential individual that doesnt even belong to an establishment of a sort).
Now you have given the example of usage of sharpshooters (the snipers). That wont work in LiF world. There is something called TeamSpeak or Skype or Mumble or whatever other voice or written chat program that doesnt actually remove the individual from the face of the LiF world, but only the character - the alter ego of that individual. That makes it just too much work for not much of a gain.
Id personally invest my time grinding something (like chopping wood like crazy) than waste my time planning and executing a rather hard mission for basically no gain.
Now to prisoners. I really, really love the idea and i wanted to (or maybe i did but i dont remember) suggest it. While it would add a totally new concept for MMO genre and add an amazing immersion factor it just might "kill" the game (at least for some).
Let me put some extreme situations (i like giving extreme situations cus i think that those are the most difficult to solve and if they are solved than all others might be much easier):
Lets put it like this; i am the king and you are the king. You manage to imprison me (or your elite squad did it or who ever else). Now what? Ransom? Why? Just keep me there and dissolve my kingdom. But that might not work because im alive, and i can still be the king. Even if game mechanics would disable my ability to "rule" i still got TeamSpeak. I would have already have sorted out who would "take" my place and i would still rule from the shadows (of my cell or something).
Lets say devs and community makes an ingenious mechanic that would make ransoms a really good choice and that the prisoner is really a prisoner so this succeeds. Then we have another problem:
Lets say i hate you cus u are on the internet and its not really rare that hatred on the internet can get to some epic proportions (i have seen it on all multiplayer game forums between various ppl) and the reasons might be totally valid or totally retarded. So, i hate u and i imprison you. I dont wan ransom. I just dont want you to play. So you have payed x$ for a game to be perma banned by another player? That is just wrong on many levels. Even if it wasnt a perma ban then i could say keep you for one hour, or 2 hours or a day? Doestn matter how long it is, it seems like players will be able to legally ban other players from the game "cus they can". Not everyone can play 27/7, some ppl maybe 1h a day (if that much even). They want to enjoy the game and they can make a mistake to provoke someone (in the game and/or on the forum) and its not hard to ambush someone and deny them even that little time they got to play it.
If you can find the solution to those problems i stated i would love to see all of those features in!
TL:DR version
Spoiler
Assassination - bad cus small gain and too much effort; no effect on organizations cus TeamSpeak
Prisoners - Pay for the game to be banned by another player?