This  combat overhaul changes locational damage and adds criticals outside VATS/VAFS, movement changes, cover effects, and some bleeding effects. No scripts. Includes optional carry-weight mutator. This mod can be installed and uninstalled at any time. The mod was basically compiled by copying methods from other mods, which are credited below.

THERE ARE TWO VERSIONS - ONE WITH CARRY WEIGHT CHANGES AND ONE WITHOUT THIS CHANGE. ONLY USE ONE.

Details

Yellow font explains the effect at a technical level and reasoning for the modification, for those who want to change the mod in xedit.

1. Locational damage modifiers are completely based on "Hit Em Where it Hurts". For instance, humans (including the PC)  take 5X more damage to the head, 1.5 more to the torso, but less to the limbs. 

This is accomplished by changing body data associated with race templates. Does not work on creatures without body data. Reverts if mod is removed. 

2. Slower human movement but faster beast movement. This is based on Immersive Fallout.

Change to basic game setting. Reverts if mod is removed.

3. Some AI changes from 4estGimp's AI Edits and Stealth and Detection system to make NPCs act better. NOTE: only some edits.

Change to basic game setting. I tried to get this to a good state but I really barely understand what all this crap does. Reverts if mod is removed.

4. Cover Simulation. When crouching, not moving, and not in power armor, you have a 15% chance of not taking damage from a single attack. This is to simulate the effect of being next to cover or "prone" in avoiding shots. Yes it doesn't make sense in melee, but just imagine that you are doing some CQ kung fu.

This is accomplished by giving a Perk Book, which grants the 2gt_PlayerPerk.  The script which gives this book is the only script used in the mod and used only once. As part of this perk, an effect is created which reduces damage to 0 with crouching w/ no PA conditions, and random check less than 15%. I could not make this into a spell, and hence there are now sound effects for when an attack "misses" (IF SOMEONE CAN FIGURE OUT HOW TO DO THIS WITHOUT SCRIPTS, BUT WITH SOUND EFFECTS, PLEASE HELP). I tested this by setting the rate to 100%... seemed to work most of the time, though some damage registers before the mod can zero-it-out.

5. Ballistic Simulation. Nothing fancy here and you can easily over-write with, say, Weapons of Fate, Armament, or AF76. The model here is basically what is used in Wasteland Ballistics but individual values are adjusted based on other mods.

This makes changes to projectile records which are modeled from several other mods. Reverts if mod is removed.

6. Criticals outside of VATS, based on the mod of the same name. Every point of Luck adds  .3% to critical chance. Every point of Perception adds .5% for rifles and pistols. Every point of Strength adds 1% for melee weapons.

This is accomplished by giving a Perk Book, which grants the 2gt_PlayerPerk. The script which gives this book is the only script used in the mod. Reverts if mod is removed. Note that no changes made to Four Leaf Clover.

7. Lite Bleed. When the Torso is less than 40%, all damaging attacks have  50% chance to create a stacking bleed effect which does 1 HP damage every tick for 30 seconds. This effects the PC and NPCs and is cured by Stimpacks and anything that uses the Stimpack effect, including Wasteland Medic. (Actually, not cured but no bleeding during the duration of the health regen effect)

This is accomplished with a perk called "2gt_CombatPerk" which is distributed to every creature and player by the "abLegendaryCreatures" spell. The perk simply inflicts a do harm on hit effect with a random chance condition and a torso health condition. Reverts if mod is removed. This is to give an immersive effect. I did not even attempt to make this more comprehensive because that would increase likely hood of things going wrong, such as having persistent  lite-bleed effects that can't be dispelled (a problem I had in MAIM, which is partially a game engine thing but still, comes about when there is more complexity in the mod)

8. Death Spiral. All actors take additional 50% damage when their torso is at 0.  In practice, this rarely occurs but it will definitely help to accelerate fights against damage large creatures.

This is accomplished with a perk called "2gt_CombatPerk" which is distributed to every creature and player by the "abLegendaryCreatures" spell. The perk simply mods incoming damage under certain conditions. Reverts if mod is removed.

9. Carry - Weight Overhaul, based on You Really Need a Backpack. This sets the base carry weight (when not wearing Power Armor) to 65 and increases this by 5 up to STR 6 (100). After that, STR does NOT increase carry weight, but Strong Back perk DOES increase it by 5 per point. Neither armor pockets nor backpacks nor anything else I found increases carry weight limit. Another note: (Strong Back does not increase the carry weight limit by 5... it sets it to 105,110,115,120; this is relevant if you have a mod which allows getting Strong Back without the STR 6 requirement.

The weight limit version is archived. This feature is better handled in other mods and sgould not need a perk-book to achieve this. I'm publishing The Great Backpack Nerf  for this effect.

Requirements, Compatibility, and Load Order

INCOMPATIBLE:

• Anything that uses  "abLegendaryCreatures" and anything that uses  perks that do "On Hit Effects". Thus, incompatible with Wasteland Ballistics and MAIM. If you want those mods, but want to keep the above AI, movement, and locational damage modifiers, load this above Wasteland Ballistics. But really... that's overkill
• Critical outside of VATS is redundant and may cause more criticals. So to is any mod that incorporates this, but that's usually very easy to disable with xedit.
  

Load ABOVE THIS MOD:

•  4estGimp's AI Edits and Stealth and Detection system, if you want the full set of tweeks but want them toned down a little.
  

Load BELOW THIS MOD:

• Anything that adds projectiles, like Weapons of Fate. The projectiles with this mod are only serviceable and you can do better.
  

Highly Recommend:

• SCOURGE. At higher levels, even the body location changes will not be enough to deal with bullet spoonges.
•  Fallsouls - Unpaused Game Menus . 
• Wasteland Medic 
• Advanced Needs 76 . Recommend set incoming and outgoing damage to around 1.3 - 1.5. NOTE: The way this mod calculates ammo weight is incompatible. Essentially, you need to either forgoe ammo weight or play on Survival without Advanced Needs 76.
  

Reasons for Making the Mod

I feel Wasteland Ballistics is great, but makes killing many creatures too easy. I don't like all the stuff MAIM adds, and more importantly, for me (and I'm just talking about my experience here), I easily got messed up and corrupted effects.

Credits:
Hit Em Where it Hurts ChoiceSpecsMawile
Immersive Fallout. zanadaniel
4estGimp's AI Edits 4estGimp (and he/she got the basis from KeyC0de)
Criticals outside of VATS NotSure700
Wasteland Medic & Wasteland Ballistics  Hedieded
Fallsouls - Unpaused Game Menus
 Improved - Animated Accessible Backpack (Stand Alone)