Personally I want more realistic stealthful killing. Even if someone screams before you kill them, you'd have ample time to run and chances are they wouldn't know who you are off the bat if you were sneaking around. And I'm pretty sure you can't pack a body roughly the same size as you in your backpack.
I'd want:
-Alarm; Someone you kill should try to raise it if they notice you before death and have ample time to raise one. IE, if they see you and you can't manage to kill them, they might have enough time to yell that they're being attacked. They might figure out who you are in the process if they have knowledge of your existence and scream that too. However, depending on the situation you can kill them halfway through the scream or before they can get it out. Witnesses that see you kill them or try to will try to raise alarm and escape, though sometimes you may get lucky and begging for you to spare them in exchange for their lives, though they may occasionally lie, depending on if you're known well. Alarm should be some sort of measured thing; People will just think nothing at first, maybe that someone is having a nightmare, then they'll grow uneasy and spread rumors, then they'll get nervous and guards will grow more alert, until you reach a breaking point where they know something is wrong and begin searching for things unusual, and begin hunting you down when they know you're lurking.
-Surprising someone and silencing them, perhaps to interrogate them. Like if your surroundings permit it, you could hide in a small nook and pull someone inside with you into a chokehold, then do needed tasks (Kill them, knock them out, interrogate them) from there.
-The adventurer noticing things; if you leave someone alive too long that has seen you that won't keep silent, something like "_______ has a sudden look of realization on their face!" will show up, or when hiding if a guard or civilian runs by your character will notice if they're alerted, such as:
"______ paces by, a nervous look on their face as they search the shadows."
"______ runs by, cursing and looking as if searching for something."
"______ looks like they're calming down from something."
-People being tipped off by unusual things; blood on the floors and walls, tables and chairs knocked over, broken objects.... If someone sees you, if you're bloody they'll get concerned.
-Bodies have to actually be HIDDEN, and can't be carried in your backpack. You can pick someone up and carry them, with the cost of being encumbered and in a bad position if attacked, or you can drag them around. People won't know they're dead until they've been missing long enough and enough evidence is present or the body is found.
In retrospect, I think I play too many stealth games and it's beginning to affect me XD