INSOMNIA FROM EPISODE ARDYN IN THE MAIN GAME

INSTALLATION:

• Copy the downloaded files and overwrite the originals in their respective folders in the FINAL FANTASY XV game directory.
• BACK UP YOUR ORIGINAL FILES BEFORE USING THIS MOD. I also included my originals as 'orig' files in each folder just in case.
• Before you replace your original files, make a save file with the bros somewhere in the city on ground level since the EPA map doesn't include the underground resting spots. If the bros aren't on ground level when you load the modded EPA Insomnia, they'll fall through the map into the void below.
• Made with the Steam version. Use at your own risk. The sky replacements all also affect the rest of Lucis since Insomnia and Lucis share the same sky.
  

ABOUT THE MOD:

• You should have the EPA DLC installed to be able to use this mod. This mod doesn't give you the DLC; it only loads the DLC data into the main game.
• Main file 'group_insomnia_ful' will replace the ruined Insomnia map in the main game with Insomnia from Episode Ardyn.
• The optional 'worldshare_system' files all replace the sky. Choose and install only one at a time.
• If you want, you can replace only the map or only the sky or both. See images for reference.
• If you only replace the sky (and/or nuke the weather system as per the update below), the quests in the ruined Insomnia will still be playable.
• If you only replace the map OR if you replace both (and/or nuke the weather system), you will not be able progress with the main quest or interact with anything aside from destroying props. There will be no NPCs or enemies either. All you'll be able to do is simply run around and take pictures.
  

UPDATE 20.12.2020 - WEATHER SYSTEM, PARTICULAR AREAS & CUTSCENES IN RUINED INSOMNIA:
So basically the dark green long-night sky is just a weather effect so you do not actually need to replace the sky to get rid of the effect (hence, I uploaded all sky replacements as optional files). You can simply disable the general weather system in the game to get the same result as with EPA Insomnia sky. Note that this will again affect both Insomnia and the rest of Lucis. To disable the general weather system, rename or move the following main weather system file:
[your FFXV directory]\datas\level\world\worldshare\environment\system\worldshare_system_climatebox.earc

The above will clear up the sky in certain parts of the ruined Insomnia. Some areas will still stay covered by the dark green sky though. No restrictions in EPA Insomnia. To clear up the sky in the entire ruined Insomnia, go to [your FFXV directory]\datas\level\dlc_ex\ful\qroup and rename/move all files with 'envsys' in their names found in the subfolders, i.e. map_insomnia_a/b/c/etc. You can simply hit Ctrl+F while in the qroup directory and search for 'envsys' to find them all at once. There should be 26 of them. Don't ask me which one affects which part of the city. I just renamed them all at once and made a quick run around the whole city to see if the dark green sky disappeared from everywhere. If you want, test the files one by one yourself.

So that takes care of the entire ruined Insomnia map but you'll still be left with the dark green sky in some cutscenes. To resolve that in the following cutscenes, rename or move the following files:

• Ardyn's meteor shower & setting up his own "wall": [your FFXV directory]\datas\level\dlc_ex\ful\share\event\gt01_03ins_10\gt01_03ins_10_light.earc
• Cerberus phase 2: [your FFXV directory]\datas\level\dlc_ex\ful\share\event\gt01_05ins_10\gt01_05ins_10_light.earc
• Cerberus phase 2 with Cor: [your FFXV directory]\datas\level\dlc_ex\ful\share\event\gt01_04ins_10\gt01_04ins_10_light.earc
• Cor saves Noctis at the end of the battle against Cerbie: [your FFXV directory]\datas\level\dlc_ex\ful\share\event\gt01_04ins_20\gt01_04ins_20_light.earc
• Daemons march towards the Citadel, Luna summons the Astrals to take them down and rekt Ardyn's wall: [your FFXV directory]\datas\level\dlc_ex\ful\share\event\gt01_06ins_10\gt01_06ins_10_light.earc
• Interdimensional nonsense aka Omega's appearance: [your FFXV directory]\datas\level\dlc_ex\ful\share\event\gt01_01omg_10\gt01_01omg_10_light.earc
  

THINGS TO NOTE:
Messing with the lighting/sky/weather will ofc affect a few other things. List of what I've noticed:

• the turquoise/blueish lighting will be gone from the fights against the past kings of Lucis
• the first stage in the Citadel where you face the Fierce has messed up lights, all bros look strangely metallic (resolve that with Nsept's Light fix mod)
• the second stage where you face the Rogue has the walls surrounding it visible while normally they're hidden in darkness
• Prompto's crackshot will literally make him and other characters glow white when you use it
• lighting will be messed up when Noctis opens the door to the throne room and for a few seconds the screen will blind you with pure white
  

Other than that, I haven't managed to locate the file(s) that control the lighting/sky while you're in the throne room so if you find it(them), please let me know. I'll add it here. Also, if you come across anything else that should be noted here, feel free to leave me a message. Thank you.