Quote Originally Posted by SinsI View Post
What if you are Tiny and facing a Huge monster? Do you really want dragons easily slain by a village of commoner Gnomes?

Second that it should reduce dex to AC, up to "flatfooted" status.
Heavily armored characters should be favored by these rules - armor has only a few weak points, and only one or two opponents have access to those Achilles Heels, the rest are actually making it harder for them to hit.

And the attackers should receive a to-hit penalty if their number is above 4 (i.e. some of them use reach weapons).
This would make it entirely circumstantial. For instance if you are wailing on a fully armored foe with bludgeoning weapon his armor may provide protection but it's still going to hurt. Your assumption works on piercing or slashing but only minimally. Take plate armor for instance. Any place where the plates come together (commonly at joints) is going to be susceptible to precision damage. These weak points would be available on most if not all sides of an opponent. Thus weakening the point of having it only effect max Dex because a overwhelmed opponent would be considerably less able to defend those weak spots.