The fundamental question might be - does the wound system really only penalize the players? If yes, don't be surprised if people will consider the book-keeping as tedious and annoying. It is done for nothing but a negative game effect.
If there is something to be gained, maybe it can be turned into something more... exciting and feel worth the book-keeping?
Bloodied is kinda already an example for that. It is not much book-keeping, but it is still there. Bloodied is by tendence something "bad" - you have less than half your hit points now! But, special effects trigger on them - sometimes they are harmful (Vampries starting to drain your blood! Ugh!) but often it's actually pretty nice, like gaining Regeneration (Shifter) or attack bonuses (Dragonborn).
So, there is a risk-reward scheme at work. Figure out a system - even if it requires book-keeping - that comes with a risk-reward scheme.
Maybe:
When you are bloodied or reduced to 0 hit points, you can accept an active wound. Example Wounds:
- Leg Injury -> Reduce speed by 2 squares and -2 to Athletics/Acrobatics
- Arm Injury -> -2 penalty to melee weapon damage rolls and Athletics/Acrobatics
- Head Injury -> -2 penalty to Perception and ranged weapon and implement damage rolls.
- Torso Injury -> -2 penalty to Endurance and -1 to all defenses.
If you have 4 or more active or inactive wounds, you take damage equal to your bloodied value when accepting another wound.
Whenever you accept a wound, you gain an action point. You can spend 1 action point per encounter, plus one additional per wound you are currently suffering from. Whenever you complete a milestone, you can spend a healing surge to gain an additional action point, once for each active wound you posess.
After each extended rest, make an Endurance check for each wound you are suffering from. The DC is hard for inactive wounds and moderate for active wounds. A succesful check drops an active wound to an inactive wound, and a inactive wound is healed. Inactive wounds only cause their penalties when you are bloodied.
When you heal an inactive wound, you can choose to gain a scar. Whenever you choose to accept a new wound, you can choose this wound to be one of your scars. If you do so, you gain temporary hit points equal to your level, but until the end of the encounter, every critical hit against you deals +1d10 points of damage per tier.
Feats
Frightening Scars
Prerequisite: You must have at least one scar.
You take a -2 penalty to Diplomacy checks, but gain a +2 bonus to Intimidate checks. Additionally, whenever you make an Intimidate Check, you can roll two d20 and take the higher result.
That Old Pain
Prerequisite: You must have at least one scar.
Once per encounter, when you accept a wound to one of your scars, you can choose to become weakened or dazed until the end of your next turn to also spend a healing surge. This weakened or dazed condition cannot be negated in any way.
This is some extra book-keeping:
- Keep track of wounds in two different states
- Make checks for recovering wounds
- Apply penalties for wounds (depending on whether bloodied/not bloodied)
- Keep track of Scars
The upside is - it's absolutely optional, you can play as if this rule didn't exist if you want to.
It has a risk-reward scheme - or rather a penalty-reward scheme. Yes, there is a penalty, but you get an action point for it! That's neat, isn't it?
