It wouldn't be if that was what happens. If they were to make it I'm sure they would come up with something more original, like an arrow completely going through someones head and leaving a gaping hole. Following an arrow in slow motion as it hits your target can give it an extra "oomph". I'm fine with adding them as long as I can set frequency and choose to turn them off completely.
I think they won't make a finisher for bows after the release of the game. Also the "hole" in the head would just be a texture, since that would be a lot of work with "changin head model script" or anything like that. An arrow slow motion sounds good to me....like "oohhhh looooook he gonna hit he gonna hit.....aaaahhh. he missed -.-" But a finisher for a bow isn't so good.