So now for my idea.
It's only a start, but I was thinking, I could just modify the current system of hit point reduction as follows (It might sound a bit like sundering worn objects):
1. Each body part recieves its own AC based off the traditional AC; however, each body part recieves a bonus to AC based on its size, using exactly the bonuses given to individual characters based on their sizes. So, aiming for the head of a medium sized character would start with an AC based on armor and dexterity, X, with an addition of the head's diminutive size (an estimate), making the total X + 4. The resulting hp damage would be multiplied by a factor of something (haven't worked this out yet).
2. Should a player fail to break the AC of the targeted body part, it is determined (secretly, by the DM) if the base AC was beaten by the player's roll. If this is so, then there will be a d% roll or something to determine which is damaged (details, details), with multiplied or reduced damage depending on the body part struck. I'm thinking about having added effects based on the damage done and by how much the player beat a roll; things like decapitation, dismemberment, impending but slow death (as with a grievous neck wound).
I still have many things to work out, and although it'd probably take way longer to figure things out, it might just speed combat, making it more realistic and deadly. I also realize the players must be subject to the same rules, which is why I'd present the idea to them and then offer a test run. Anyways, thoughts, suggestions, descriptions of previous experience with this sort of thing are all welcome.