Why?

I was inspired to make this mod because of the excellent mhg custom quest pack , which has some quests that take place in the challenge arena. While the quests in the pack are meant to be a significant challenge, the arena quests are seemingly randomly spread between the special arena and the challenge arena, and I was getting a bit annoyed that a single faint halfway through a fight meant I couldn't restock my buff items on those quests. I may try to add a meal chair somewhere in the future, if I can figure out how to do that. Of course, this mod modifies the challenge arena for all quests (including vanilla), which I will get into in the next section. 

Caveats

Because the stage files are being modified directly, the item box will be accessible in arena counter quests from the arena lass, which means you can swap item loadouts or equipment loadouts in these quests and effectively cheat them. I don't suggest you do this, so if you really want to you're proceeding at your own risk. As well, some of the options like changing layered armor can make your game crash and swapping equipment loadouts turns your weapon invisible until the end of the quest, but I never intended on making the mod for these purposes. Swapping decos out works fine.

To be very clear, I made this mod with the intention of only restocking my item pouch during regular non-arena-counter quests, and I suggest you only use it for the same reason. It (probably) won't mess up your save if you use it for other reasons, but of course, I am not responsible for any damage this might do if you use the other options in the box.

Installation/Uninstallation

Just like every other mod, unzip the mod and drop the nativePC into your root MHW folder (alongside MonsterHunterWorld.exe). I use stracker's loader and performance booster plugin, which should be the bare minimum for loading mods in most cases.

If you're prompted to merge folders, go ahead, but if you're being asked to overwrite files (st202.sobjl, etc.) when you install this mod, you probably have a mod that's already changing the arena stage in some way. This mod won't be compatible with your existing mods in that case.

To uninstall, remove the following files from the mod directory (nativePC/stage/st202/common/set/):
st202.sobjl
st202_gm.sobj
st202_ib.sobj


Thank you
Thank you to Dave uRrr for the great 010 templates and tutorial on sobj editing (link)
Thank you to the MHW modding discord for having a plethora of existing answers to the questions I ended up having myself
Thank you to everyone who developed tools for making MHW modding easier (MHWNoChunk, etc.)