This sure is somewhat realistic, but gameplaywise I have 2 thoughts:
1. I think there already is enough depth in melee fights. Right now it includes e.g. blocking, feinting, chambering, timing, range control, footwork, kicking and even that applies different for different weapons. Even without the implementation of your suggestion, meaning with even less aspects of melee to be familiar with, I dont know anyone yet winning 100% of all 1v1 duels due to the melee system being to easy to master. If 50% of all duels took more than 3 minutes you'd know providing melees with some new techniques is in need. But thats not the case I guess.
2. How would you counter it ? Right now you cant really controll the armmovement or elevation of a sideblock, so your charged high blows would stun enemies to a 100% basicly letting the player with more weapon range win.