Presets:
Moderate: Recommended if you think the vanilla mechanics are all fine and you don't want too much challenge, but you believe the monsters die a bit too fast.
Hard: The way I believe the game should have been from the start. Should play well across all stages of progression.
Very Hard: "We have Master Rank at home" but you're not wearing Master Rank equipment. Plays well if you are at endgame with good builds. Great for farming HR and not getting bored.
Nightmare: If you want to test yourself. Many of the stronger attacks by tempered monsters become one-shots here even on endgame builds, endgame hunts become fairly unforgiving and taxing.


Changes:
Increased Monster HP and damage, varying by preset
Moderate: 40% more HP, 10% more damage
Hard: 60% more HP, 30-50% more damage
Very Hard: 100% more HP, 60-80% more damage
Nightmare: 150% more HP, 100-120% more damage

Lower difficulty monsters have bigger damage increases than higher difficulty monsters. This makes the difficulty curve smoother and ensures lower rank monsters can at least still hurt you.

Wound/part resistance has been adjusted accordingly to HP changes to prevent frontloading all wound and part breaks at the beginning of the hunt. This makes for longer hunts where the monster is active for longer and tends to suffer less from perma-stunlock syndrome due to the wound system. You will see (and need to deal with) more of the monster movesets in any given hunt, scaling with the preset.

Increase rate of HR points from surveys and investigations. NOTE: This seems to not apply to pre-made quests, such as story, assignments, and event quests. 
Moderate: 20% more
Hard: 40% more
Very Hard: 80% more
Nightmare: 120% more

Palico healing and tool nerfs. Palicoes will now heal you less often, and for less health. If you see your Palico coming to heal you, it's a good time to move away from the monster and stack your own healing potion into it for a full heal. You now cannot expect to keep hitting the monster while still getting fully healed by your Palico. Does not apply to Moderate. Further nerfed on Nightmare.

Mantle duration nerfs. Does not apply to Moderate.

Reworked Potions. They now have most of their healing backloaded at the end of the animation, with the animation also lasting slightly longer, meaning if you get interrupted or roll away you will waste the vast majority of their value. To somewhat compensate for the longer animation and the increased incoming monster damage, potions also heal for around 15% more. This change overall makes it more punishing to attempt to heal at a bad time. Does not apply to Moderate. 

Experimental Seikret AI adjustments during combat. Does not make a big difference as of now, but something to update in the future. The goal is to keep the Seikret further away from the hunter during combat, but this has shown to have inconsistent results. Does not apply to Moderate.

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Installation: 
1. Install RE Framework
2. On first boot after installing RE Framework, press Insert, open the LooseFIleLoader section, and check "Enable Loose File Loader"
3. Close the RE Framework window to make sure your changes are saved. THEN close the game.
4. Drop the "natives" folder from your chosen preset to the base directory of Monster Hunter Wilds
5. Boot the game up again. If you want to make sure the mod loaded, press Insert again and check the LooseFileLoader section, if it loaded additional files after installing the mod then you are good to go. For the presets higher than Moderate you can also check if the potion changes have applied.

"Hey can I have X part but not Y part? Can I have only this aspect from preset X but with that aspect from preset Y?"
YES! The files are mostly modular, you can remove parts you don't want by deleting files, or mix and match them from different presets. The presets are balanced around my idea for difficulty selection, but you can mod your game however you want. Here is a list of what each file does so you can customize the mod:

Enemy\CommonData\Data\EmCommonDifficulty2.user.3
Controls enemy damage and HP. 

Mission\_UserData\_Reward\RewardRateData.user.3
Controls the HR point rates for investigations

Otomo\DataParam\OtomoToolParam.user.3
Controls the Palico tool usage

Player\ActionData\Common\GlobalParam\Part\PlayerActiveSkillParam.user.3
Controls the Mantle durations

Player\ActionData\Common\GlobalParam\PlayerItemParam.user.3
Controls the potion changes

Porter\Data\PorterParamCommon.user.3
Controls the Seikret changes. Delete this if it bugs out LOL


DISCLAIMER: I do not condone using this mod online with random strangers. There is still a lot unknown about how gameplay mods affect multiplayer. Remember, no one has consented to mods being used in their lobbies and quests, be nice and don't use mods online unless you are playing with your friends or otherwise people who know what mods you are using and consent to their usage. To turn mods off temporarily, simply rename the "natives" folder in your game directory to anything else before booting the game, then name it back to "natives" once you want to boot the game modded.

Also, I don't have a ton of time for modding, I mod mainly for myself. This means that I won't be checking comments too often, and I won't be able to adjust things or do requests. Additionally, if a game patch breaks the mod and I happen to be busy, just assume the mod is not getting updated anytime soon. This mod is just simple edits to game files, so feel free to modify it, reupload it (in the event you update it for a new game version, for example), or use any of these edits and ideas on any of your mods. Credit would be nice but not required.


CREDITS:
Synthlight for his excellent MHWS Editor mod, which was the main tool used for creating this mod.
Furiante for making the first mod of this kind: Hard(er) Mode - Increased Difficulty and helping me with modding questions. His mod is also a great alternative to this one if you want more options in terms of monster HP and damage, he offers way more presets (they can be combined into this mod).