Huge swords to at least do concussive force if blocked

[Kent]

Those largest of swords: Greatsword, Flamberge, Claidhmore, and the like need two hands to wield and they strike only once per round. It only seems right that if these massive swords are blocked by a shield, they should at least do some concussive damage and not have the shielder get off scot-free.

Truth be told, I would even like to see a chance of the shield being split....but that's for another day.