Entire Rework of how I've done this

Call this shit "Armor 2"

code/modules/mob/living/simple_animal/_damage_coeff.dm

@@ -0,0 +1,96 @@
+#define DAMCOEFFID "damage_coeff-[red]-[white]-[black]-[pale]-[brute]-[burn]-[tox]-[clone]-[stamina]-[oxy]"
+
+/proc/getDamCoeff(red = 1, white = 1, black = 1, pale = 1, brute = 1, burn = 1, tox = 1, clone = 1, stamina = 1, oxy = 1)
+	. = locate(DAMCOEFFID)
+	if(!.)
+		. = new /datum/dam_coeff(red, white, black, pale, brute, burn, tox, clone, stamina, oxy)
+
+/proc/makeDamCoeff(list/dc = list())
+	var/brute = 1
+	var/burn = 1
+	var/tox = 1
+	var/clone = 1
+	var/stamina = 1
+	var/oxy = 1
+	var/red = 1
+	var/white = 1
+	var/black = 1
+	var/pale = 1
+	for(var/I in dc)
+		switch(I)
+			if(BRUTE)
+				brute = dc[I]
+			if(BURN)
+				burn = dc[I]
+			if(TOX)
+				tox = dc[I]
+			if(CLONE)
+				clone = dc[I]
+			if(STAMINA)
+				stamina = dc[I]
+			if(OXY)
+				oxy = dc[I]
+			if(RED_DAMAGE)
+				red = dc[I]
+			if(WHITE_DAMAGE)
+				white = dc[I]
+			if(BLACK_DAMAGE)
+				black = dc[I]
+			if(PALE_DAMAGE)
+				pale = dc[I]
+	return getDamCoeff(red, white, black, pale, brute, burn, tox, clone, stamina, oxy)
+
+/datum/dam_coeff
+	datum_flags = DF_USE_TAG
+	var/brute
+	var/burn
+	var/tox
+	var/clone
+	var/stamina
+	var/oxy
+	var/red
+	var/white
+	var/black
+	var/pale
+
+/datum/dam_coeff/New(red = 1, white = 1, black = 1, pale = 1, brute = 1, burn = 1, tox = 1, clone = 1, stamina = 1, oxy = 1)
+	src.red = red
+	src.white = white
+	src.black = black
+	src.pale = pale
+	src.brute = brute
+	src.burn = burn
+	src.tox = tox
+	src.clone = clone
+	src.stamina = stamina
+	src.oxy = oxy
+	tag = DAMCOEFFID
+
+/datum/dam_coeff/proc/modifyCoeff(red = 0, white = 0, black = 0, pale = 0, brute = 0, burn = 0, tox = 0, clone = 0, stamina = 0, oxy = 0)
+	return getDamCoeff(src.red+red, src.white+white, src.black+black, src.pale+pale, src.brute+brute, src.burn+burn, src.tox+tox, src.clone+clone, src.stamina+stamina, src.oxy+oxy)
+
+/datum/dam_coeff/proc/setCoeff(red, white, black, pale, brute, burn, tox, clone, stamina, oxy)
+	return getDamCoeff((isnull(red) ? src.red : red),\
+					(isnull(white) ? src.white : white),\
+					(isnull(black) ? src.black : black),\
+					(isnull(pale) ? src.pale : pale),\
+					(isnull(brute) ? src.brute : brute),\
+					(isnull(burn) ? src.burn : burn),\
+					(isnull(tox) ? src.tox : clone),\
+					(isnull(clone) ? src.clone : clone),\
+					(isnull(stamina) ? src.stamina : stamina),\
+					(isnull(oxy) ? src.oxy : oxy))
+
+/datum/dam_coeff/proc/getCoeff(coeff)
+	return vars[coeff]
+
+/datum/dam_coeff/proc/getList()
+	return list(RED_DAMAGE = red, WHITE_DAMAGE = white, BLACK_DAMAGE = black, PALE_DAMAGE = pale, BRUTE = brute, BURN = burn, TOX = tox, CLONE = clone, STAMINA = stamina, OXY = oxy)
+
+/datum/dam_coeff/vv_edit_var(var_name, var_value)
+	if (var_name == NAMEOF(src, tag))
+		return FALSE
+	. = ..()
+	tag = DAMCOEFFID // update tag in case damage_coeff values were edited
+
+#undef DAMCOEFFID

code/modules/mob/living/simple_animal/damage_coeff_helper.dm

@@ -86,7 +86,29 @@
  * * TRUE if value was successfully changed.
  */
 /mob/living/simple_animal/proc/ChangeResistance(resistance, value, update = TRUE)
-	unmodified_damage_coeff[resistance] = value
+	switch(resistance)
+		if(BRUTE)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(brute = value)
+		if(BURN)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(burn = value)
+		if(TOX)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(tox = value)
+		if(CLONE)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(clone = value)
+		if(STAMINA)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(stamina = value)
+		if(OXY)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(oxy = value)
+		if(RED_DAMAGE)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(red = value)
+		if(WHITE_DAMAGE)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(white = value)
+		if(BLACK_DAMAGE)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(black = value)
+		if(PALE_DAMAGE)
+			unmodified_damage_coeff_datum = unmodified_damage_coeff_datum.setCoeff(pale = value)
+		else
+			return FALSE
 	if(update)
 		UpdateResistances()
 	return TRUE
@@ -95,32 +117,46 @@
  * Updates all of a mob's resistances to be based on their base value with modifiers added.
  */
 /mob/living/simple_animal/proc/UpdateResistances()
-	damage_coeff = unmodified_damage_coeff.Copy() // Reset resistances
+	var/list/cached_resistances = unmodified_damage_coeff_datum.getList() // Reset resistances
 	for(var/datum/dc_change/D in damage_mods) // Check our multiplicative mods
 		if(D.additive)
 			continue
 		if(islist(D.damage_type))
 			for(var/dam_type in D.damage_type)
-				if(damage_coeff[dam_type] <= 0) // Immunity / Healing is not modified
+				if(cached_resistances[dam_type] <= 0) // Immunity / Healing is not modified
 					continue
-				damage_coeff[dam_type] *= D.potency
+				cached_resistances[dam_type] *= D.potency
 		else
-			if(damage_coeff[D.damage_type] <= 0) // Immunity / Healing is not modified
+			if(cached_resistances[D.damage_type] <= 0) // Immunity / Healing is not modified
 				continue
-			damage_coeff[D.damage_type] *= D.potency
+			cached_resistances[D.damage_type] *= D.potency
 	for(var/datum/dc_change/D in damage_mods) // Then include additive modifiers
 		if(!D.additive)
 			continue
 		if(islist(D.damage_type))
 			for(var/dam_type in D.damage_type)
 				if(damage_coeff[dam_type] <= 0) // Immunity / Healing is not modified
 					continue
-				damage_coeff[dam_type] += D.potency
+				cached_resistances[dam_type] += D.potency
 		else
 			if(damage_coeff[D.damage_type] <= 0) // Immunity / Healing is not modified
 				continue
-			damage_coeff[D.damage_type] += D.potency
+			cached_resistances[D.damage_type] += D.potency
+
+	for(var/I in cached_resistances)
+		cached_resistances[I] = round(cached_resistances[I], 0.1) // Minimizes damage_coeff datums created due to rampant decimals.
 
+	damage_coeff_datum = damage_coeff_datum.setCoeff(
+		cached_resistances[RED_DAMAGE],\
+		cached_resistances[WHITE_DAMAGE],\
+		cached_resistances[BLACK_DAMAGE],\
+		cached_resistances[PALE_DAMAGE],\
+		cached_resistances[BRUTE],\
+		cached_resistances[BURN],\
+		cached_resistances[TOX],\
+		cached_resistances[CLONE],\
+		cached_resistances[STAMINA],\
+		cached_resistances[OXY])
 
 /**
  * Give it a dc_change modifier path and it will check aganist that. If it exists in the list, it will be returned.

code/modules/mob/living/simple_animal/damage_procs.dm

@@ -22,60 +22,60 @@
 /mob/living/simple_animal/adjustBruteLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[BRUTE])
-		. = adjustHealth(amount * damage_coeff[BRUTE] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.brute * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustFireLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[BURN])
-		. = adjustHealth(amount * damage_coeff[BURN] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.burn * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustOxyLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[OXY])
-		. = adjustHealth(amount * damage_coeff[OXY] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.oxy * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustToxLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[TOX])
-		. = adjustHealth(amount * damage_coeff[TOX] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.tox * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustCloneLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[CLONE])
-		. = adjustHealth(amount * damage_coeff[CLONE] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.clone * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustStaminaLoss(amount, updating_health = FALSE, forced = FALSE)
 	if(forced)
 		staminaloss = max(0, min(max_staminaloss, staminaloss + amount))
 	else
-		staminaloss = max(0, min(max_staminaloss, staminaloss + (amount * damage_coeff[STAMINA])))
+		staminaloss = max(0, min(max_staminaloss, staminaloss + (amount * damage_coeff_datum.stamina)))
 	update_stamina()
 
 /mob/living/simple_animal/adjustRedLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[RED_DAMAGE])
-		. = adjustHealth(amount * damage_coeff[RED_DAMAGE] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.red * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustWhiteLoss(amount, updating_health = TRUE, forced = FALSE, white_healable = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[WHITE_DAMAGE])
-		. = adjustHealth(amount * damage_coeff[WHITE_DAMAGE] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.white * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustBlackLoss(amount, updating_health = TRUE, forced = FALSE, white_healable = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[BLACK_DAMAGE])
-		. = adjustHealth(amount * damage_coeff[BLACK_DAMAGE] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.black * CONFIG_GET(number/damage_multiplier), updating_health, forced)
 
 /mob/living/simple_animal/adjustPaleLoss(amount, updating_health = TRUE, forced = FALSE)
 	if(forced)
 		. = adjustHealth(amount * CONFIG_GET(number/damage_multiplier), updating_health, forced)
-	else if(damage_coeff[PALE_DAMAGE])
-		. = adjustHealth(amount * damage_coeff[PALE_DAMAGE] * CONFIG_GET(number/damage_multiplier), updating_health, forced)
+	else
+		. = adjustHealth(amount * damage_coeff_datum.pale * CONFIG_GET(number/damage_multiplier), updating_health, forced)

code/modules/mob/living/simple_animal/simple_animal.dm

@@ -82,11 +82,13 @@
 	var/armour_penetration = 0
 	///Damage type of a simple mob's melee attack, should it do damage.
 	var/melee_damage_type = RED_DAMAGE
-	/// 1 for full damage , 0 for none , -1 for 1:1 heal from that source.
+	/// 1 for full damage , 0 for none , -1 for 1:1 heal from that source., Modifying this variable post-Initialize is pointless.
 	var/list/damage_coeff = list(BRUTE = 1, RED_DAMAGE = 1, WHITE_DAMAGE = 1, BLACK_DAMAGE = 1, PALE_DAMAGE = 1)
-	/// A copy of the original damage_coeff, what the base resistances of a simple animal should be before modifiers.
-	var/list/unmodified_damage_coeff = list()
-	/// The datum modifiers to
+	/// The datum that stores the damage_coeff post Initialize()
+	var/datum/dam_coeff/damage_coeff_datum
+	/// The unmodified values for the dam_coeff datum
+	var/datum/dam_coeff/unmodified_damage_coeff_datum
+	/// The list of all modifiers to the current DC datum
 	var/list/damage_mods = list()
 	///Attacking verb in present continuous tense.
 	var/attack_verb_continuous = "attacks"
@@ -202,16 +204,20 @@
 		emote_see = string_list(emote_hear)
 	if(atmos_requirements)
 		atmos_requirements = string_assoc_list(atmos_requirements)
-	if(damage_coeff)
+	if(LAZYLEN(damage_coeff))
 		damage_coeff = string_assoc_list(damage_coeff)
+		damage_coeff_datum = makeDamCoeff(damage_coeff)
+		unmodified_damage_coeff_datum = makeDamCoeff(damage_coeff)
+	else
+		damage_coeff_datum = getDamCoeff()
+		unmodified_damage_coeff_datum = getDamCoeff()
 	if(footstep_type)
 		AddComponent(/datum/component/footstep, footstep_type)
 	if(!unsuitable_cold_damage)
 		unsuitable_cold_damage = unsuitable_atmos_damage
 	if(!unsuitable_heat_damage)
 		unsuitable_heat_damage = unsuitable_atmos_damage
 
-	unmodified_damage_coeff = damage_coeff.Copy()
 
 /mob/living/simple_animal/Life()
 	. = ..()

lobotomy-corp13.dme

@@ -2668,6 +2668,7 @@
 #include "code\modules\mob\living\silicon\robot\robot_modules.dm"
 #include "code\modules\mob\living\silicon\robot\robot_movement.dm"
 #include "code\modules\mob\living\silicon\robot\robot_say.dm"
+#include "code\modules\mob\living\simple_animal\_damage_coeff.dm"
 #include "code\modules\mob\living\simple_animal\animal_defense.dm"
 #include "code\modules\mob\living\simple_animal\constructs.dm"
 #include "code\modules\mob\living\simple_animal\corpse.dm"