Would need to change all the current shield stats, and the shield skill bonus.
And i'm not sure if it's worth it.
Why not just add a couple more 0 shield skill shields ?
On the other hand, if shield's difficulty was strength, we would see way less Agi High shield skill + dagger.
As for the shield bash, since it's unblockable, i don't see why it should get a damage boost. I'm already so annoyed when fighting a shielder, not even trying to attack until he can bash again.
Lastly, this change would actually fuck up throwers :
1. They have way less ammo than regular range (archers + xbow), so any ammo wasted on a shield hurts them.
2. They have crap range, so it's difficult to catch an unaware opponent. Even if it's a 2h or Polearm, he'll have time to take out his 0 shield skill shield and then walk to us.
3. Hybrid throwers would not benefit at all from thoses shields (for example a 2h/thrower with jarids, using up all his jarids, would technically have 2 free slots. BUT, unless it was fixed, the 0 ammo still take slots...)
4. Huge buff to dedicated turtle shielders. Since all shields can be taken by all players, it will be far easier for thoses guys to pick up shields on the battlefield, and you'll need another dozen of attacks to break it again, then they'll run away again to find another shield, etc...
All in all, i'm really not in favor of that change. It's not that much build-breaking to put 1-3 points in shield skill, and carry a decent shield with it, just for thoses pesky range. Stop trying to be min-maxers with your perfect optimized melee build, and complain about range.
So, why not do a double requirement : strength AND shield skill ? Since most builds would have 9 STR at least.