Kind of silly to think of a melee character just turning around every time a ranged character shoots at them.
However, I would be all for this if they removed the massive invisible shield that protects shielders. Being a good shot, I would love it if shots to the forehead actually counted (please put the higher chance to penetrate shields with crossbows back in). Honestly I think removing the invisible shieldwall would tip the favor too much towards ranged, balance wise. So I'm sure the back block won't be approved and the invisible shieldwall that protects horse's chests will remain in the game.
They could make it to where shielders standing next to each other getting the +shield message get levels of the invisible wall back, to balance it out. Would probably still not be balanced enough for non teamwork situations though(for our audience).
Also, shots that would have been a headshot should do a small amount of damage to the shield. Because usually anything less than an Arbalest does almost no damage to a good shield. Think of all the times you've seen a shield with tons of arrows/bolts in it.