Anyone played Metal Gear Rising? Doesn't it have a similiar combat? ›››
In my opinion, they have done a great deal to improve combat, increase combat animation, fine tune the targeting system etc, the natural progression would be to avoid a system that pauses or causes an interruption to the combat.
They could implement the special moves only once the monster is at certain weakness level, as more a finishing move type scenario, whereas the player without the monster research has to continue fighting in the current fashion.
The special moves could be signified by Geralt's witcher senses, with a combination of Geralt speaking 'Hmm, his left leg looks weakened and exposed'. The player could then choose to select the special move, not by a prompt on screen but by the key mapped to a special move. If the player wants to continue fighting as they are, they don't bother selecting the key mapped to the special move.
In regards to the VATS slow-mo system, I'm sure they could make this scenario work as well, but I'd prefer it if they didn't go down this path.