I think it would be good depending how it was done.
Maybe not exactly like vats.But say when the enemies HP is really low,meaning the games knows one more hit from your sword.arrow.spell etc,would kill the said enemy.
It would slow the last blow down & give you a cinamatic kill of that last blow from a different angle in slow motion.
Say your last arrow...you could watch it possibly pin someone to something or watch it peirce their head etc in slow motion.
Or a sword being thrust through the body,or head being chopped off....or you could watch someone fall of a cliff in slow motion with maybe by a spell or shield bash.
There could be many ways to do it & it would be very satisfying in my opinion,just dont do it like vats,but get the cinamatic feel of the kill.
Imagine your last fireball or lightning bolt,burning or shocking your enemy in slow motion.
I'm sure there could be a way without breaking the game...& i'm sure others maybe have better ideas than i about it