As much as I know,grappling is used in martial arts with your bare hands and foots,not with weapon,so I'm not sure how could you implement it in cRPG
my suggestion is make a chain with the hook as a new 1h/2h weapon so that you can hook an enemy,and drag him to yourself,specialy good against fleeing archers and other range bundle of stickss,the crosshair for it would be like for throwing,maybe a bit better and while doing it you would be vulnerable to anyone or anything like missiles in which case you would stop with drag animation (about damage,maybe something minimal,like that freaking Torch with 8 blunt damage,it would be mostly support weapon)
I'm not sure is this possible,or would it be fair and balanced but I just can't imagine grappling to be added because that's for martial art not medieval combat