It does not matter how you do critical hits if they are still random, while still being the only way to win the combat.
The reason why I thought headshots only in short range was because they would provide risk-reward situation. Being close to enemy is always riskier but the reward is more damage. It's used in many games and is very working feature because it encourages players to move forward instead of camping. Plus it would be bonus for pistolero characters because they are normally disadvantaged against maxrange snipers.
In addition head/eyes are the "best" target for snipers because it has the highest critchance and most severe effects. There doesn't need to be "best" target to aim at.
Btw, dunno if anyone uses the targetting doll anymore. It's all hotkeys these days.
Crit damage & effect could actually be directly related to character's luck, endurance and armor. In addition gun's strength req could pay a role, because the more powerful gun, the better effects. But powerful guns have higher ap cost, whereas lighter guns get to shoot more.
So when you got 1 luck, end and no armor, you get most damage and worst effects. When luck and END are 10, you get least damage and least harmful effects. The effects and damages could be pretty much solid so that when player wears a suit of armor and checks his stats, he will know what kind of effects will take place if he gets hit in specific location. But he can't know what gun and perks his enemy will have.
Shooter's crit chance would add more damage and better crits perk adds more effect.
What comes to cripples, they could stack. If you get hit in the arms more and more, your weapon handling strength drops. If it drops below gun requirement, there will be gundrop. If it drops down to one, you get total cripple. Enduring or high strength characters could ignore the first few armshots.
Legshots could drop your carryweight so that you will become overburdened eventually. When you have no carryweight, it counts as crippled leg.
I guess stimpaks and FA could be used to heal these stat decreases, but not cripples.
Groinshots could ignore END in terms of effects. Could be used against "anticrit" characters.