The idea is simple in concept though, since im no modder, i can only assume it isnt easy to accomplish.

1) the idea is that once the enemy has a low health and he is staggering the player can deliberatly innitiate a special finishing move (kill move) by doing a combination of key presses, like in fighting games a la mortal kombat.

so for example if the enemy is a powerful draugr but his health is really low the player can do "forward, forward, back, forward, power attack" and innitiate a certain finishing move. different combination unleashes different finishing moves.

2) a simple idea is that a finishing move does more damage than a normal power attack and takes more stamina but if the player believes he can finish off an enemy with it than he can do a specific key press combination (the same combination for all finishing moves) and unleash it. if the enemies health is low enough than the stamina waste is not in vain and a finishing move will be executed, though the player will be vulnerable to attacks of other enemies that are around him. it's a risk vs reward.

3) a more complicatedd idea perhaps can be achieved if a finisher animation can be applied in the middle of combat WITHOUT any relation to the enemy, so like in fighting games u can do a powerful move and miss if the enemy is blocking or not in range.
so if i do a specific key presses like "back, back, left , right, power attack" i can unleash the "jump and stab in the chest" type of animation (if im using a sword) and my character will do this animation. if im in range than i will hit the enemy. if im out of range than the enemy won't get hurt. either way the enemy doesnt have to innitiate his own "im hit" animation. just a normal staggering animation like from any power attack. these special attacks are more powerful, more stamina costly and more cumbersome to execute.

as far as i know skyrims animation system hasnt been fully understood yet and maybe the last idea is too far fetched, but maybe the second one is feasable but allowing certain key presses to up the chanes of a finishing move temporarily to 100% only on enemies that have low health or something of that sort.

any thoughts?

Not Mortal Kombat dudebro.

I would be OK with a specific button for finishers, but not key combinations. Hold X, perform finisher. Perhaps let the player select the finisher they want to use.

The next thing is to give it a reason for being. Making it a game mechanic doesn't make sense unless I have a reason to do it (outside of the cool-factor). Such as, maybe tie it to bullet time; make one kill, slow down, make another kill, attempt to keep the chain going.

Point 2) sounds good as well, but may lead to just leading off with finishers at the outset of the fight, and then continuously doing them by virtue of stamina potions. If there was a mobility / time cost associated, that might balance things out.

i think that if the finishers can only be done at certain times (like when an enemy is staggering or right after a power attack) and they take all remaining stamina than this could indeed be done as a way to finish of an enemy. if during the finishing animation the player is vulnerable than it is probably not a good idea to use them in a middle of a fight but only at the last enemy. also at the wrong distance the animation \ finisher can be botched and fail, leaving the player with no stamina. its like a more powerful power attack. that's it. it can fail.
a lot of ppl use mods that make kill moves more frequent. with this idea not only they can enjoy more frequent finishers but they will have gameplay mechanic attacked to it.

I like this idea. But I think that finishing moves should only work on opponents when they are under 50% health, staggered, and low on Stamina. Enemies than can be killed in one hit? I don't see the point of a kill-cam for garden variety beast and thugs.

The OPs idea of user controlled finishing moves is a great one. I find that the randomness of the vanilla finishers rarely fits the situation or my need for bloody satisfaction. For example, finishers rarely happen at the end of epic bouts, when blood lust and vengeance is very high because the damage relative to HP pool is always going to be small. Likewise, it nearly always fires against super weak opponents that just happened to walk in front of my blade because I can easily strip more than half (or ALL) of their HP with one normal attack.


EDIT:

WWMKD? is the question every kombat game designer should ask themselves when trying to make an epic fighting game with mortal characters, even one with RPG elements.