In Extra Credit’s video Like a Ninja – What Makes a Good Stealth Game, they mention that these mechanics are “all just tools in the player’s belt. They are logical functions which can be applied to the problems at hand”. Therefore, the player must use these tools the game has provided to succeed in their mission. It is highly recommended to watch their video to understand how to implement tools and mechanics for the purpose of stealth games.
An important element of air assassinations is thinking about the height of drops. It would not seem realistic if the player were to survived a long fall, but if they were to takedown an enemy at the end of that fall, their body’s momentum will be absorbed by the enemies body, providing some realistic sense but also allow for the assassination to be very rewarding by surviving. It would not be fun, or even worth attempting to do, if player ends up killing themselves in the end, thus allowing this extreme risk to become a more personal reward towards the player.