Armor optional rule for D&D and OSR games

This simple rule gives more value to armor since it adds Damage Reduction when the character would go to less than 0 hp.

RULE

Armor works normally (give AC bonus) until the character goes to 0 hp then Armor absorb excess damage from that hit.

Note: This damage reduction works only on the hit that would take the character below 0hp, if the character is already out of combat the damage reduction doesn't work, so if attacked again you apply the normal rules against helpless target.

The Damage Reduction given by armors will be equal to their armor bonus. Let's call this damage reduction (DR) a DR at Zero hp (or DRZhp).

Example: Rodrick a 3rd level fighter with 21 hp and a chain mail has +5 bonus to AC (and so also 5 DRZhp), in a long fight is reduced to 4 hp, then he is it for another 8 points of damage. Normally this would take Rodrick to -4 hp and on his way to Walhalla, but with this rule Rodrick will go to 0 hp since the additional 4 hp of damage will be absorbed by his chain mail.

NOTE: for 5th edition and 0th edition
If the rule system don't makes big distinction between 0hp and dying this rule must be modified. The damage reduction (if sufficient) puts the character at 0hp unconscious and stable (and out of the fight unless healed) but not dying. Further attacks ignore DRZhp.

Armor table

Armor	AC bonus	DRZhp
Padded	+1	1
Leather	+2	2
Studded	+3	3
Scale	+4	4
Chain	+5	5
Banded	+6	6
Half Plate	+7	7
Full Plate	+8	8

Note: Wearing an helmet will add to the DRZhp as follow
Leather cap +1 (-1 to perception)
Metal cap +2 (-2 to perception)
Full Helmet +3 (-3 to perception)

Option: if the armor reduction is used the armor is damaged and needs repairs.

Compatibility: this rule works with every edition of D&D (original, b/x, becm, rc, AD&D 1st, AD&D 2nd, D&D 3rd, D&D 3.5, Pathfinder, D&D 4th and D&D 5th) and with all retroclones that use normal AC as originally presented in D&D games (Adventurer Conqueror King System, Swords and Wizardry, Basic Fantasy RPG, Adventures Dark and Deep, Fantastic Heroes & Witchery, OSRIC, Labyrinth Lord, Dark Dungeons, Darker Dungeons, Dangers & Dweomers... and countless others). 

Design Notes

It's some time that I keep thinking about modifying how armor works, last time I took the route of critical hits ranges based on armor type OSR critical hit based on armor, this time I want to take a different approach.
The approach is to take a little further the basic idea that Hit Points are not Body Points (argument touched with the article on Death and Dismemberement article Morte & Mutilazione un nuovo significato dei punti ferita) as pointed out in so many description of hit points, read for example the explanation found in the Injury and Death in 3.5 SRD

What Hit Points Represent
Hit points mean two things in the game world: the ability to take physical punishment and keep going, and the ability to turn a serious blow into a less serious one. 

Effects of Hit Point Damage
Damage doesn’t slow you down until your current hit points reach 0 or lower. At 0 hit points, you’re disabled.
At from -1 to -9 hit points, you’re dying.
At -10 or lower, you’re dead.

Which is perfectly compatible with what Gary Gygax wrote in the Ad&d 1st edition Dungeon Master's Guide (and using the Hovering on Death's Door optional rule):

So I thought to mix the Armor Class bonus of Armor with Damage Reduction (something already suggested in the d20 3.5 srd Armor as Damage Reduction and also in the Pathfinder SRD Armor as Damage Reduction), my original addition to this is to use such reduction ONLY when the character would go to less than 0 hp.

Obviously the minimum for this system to work is that at 0 HP the character is out of combat and at -1 or worse the character is dying or dead, this means that until that last blow the character was not really hit but somehow managed to deflect or dodge the blunt of the blow, while the killing blow is somewhat reduced by the armor worn.


Why all of this?

Well there are at least two reasons:

1. I wanted to give more importance to armor without changing the way combat and damage normally works
2. I wanted to give reasons to wear armor even if the AC is naturally better (since I am thinking of adding AC bonus based on class and level)

Did I make it? Hope so!

Any comment will be appreciated.

NOTE: I'am flattened. I posted this around 13.15 local time (on August the 11th 2017), at 15.57 local time I am at 3246 visualizations... and counting... this is going to be my best blog post ever. And indeed at 16.25 local time (3h and 10 minutes it became the most viewed post of this blog ever! Surpassing post that are here since a long time ago).

NOTE2: 4343 views in 4h... this is awesome!

24 hours update: 8960 hits <3

10'000+: in less than one week (today is 16/08/2017 and we are beyond 10'000) :-)

Thank you! Thank you! Thank you!