They could have it like Halo: Reach. But here's my idea:

If you are undetected and use a normal attack, it is the same as oblivion. If you use a power attack, you preform an assassination move. High and Low profile depend on the weapon (can't knife a guy with a hammer)
High Profile Weapons: Longsword, Hammers, Axes
Low Profile Weapons: Daggers, Shortswords, Arrows (stab them, not shoot)
As for a bow, maybe a High Profile and you strangle them with the string?
High Profiles will alert anyone nearby as the target will cry out for help. Low Profiles make the body drop down quietly.


Morrowind's Remove Corpse should return too.