It is the apocalypse after all.

Here's the tedious way, which requires only a hex editor and reckless abandon of optimization:

Well this work, I thought the "remove item X from inventory" was subtracting 1 from the current item quantity, that's why I didn't thought the event route was the most practical one. Even then, you could with notepad++ and uses or copy/paste/replace write the event hex of 99 times a removal of 1 on 255 items. It's juist that it would take about 5000 bytes of free space lol

No, you're right, it is only subtracting one item from the inventory.  The loop I wrote runs 100 times, each time subtracting 1 from each item index 0 to FE.  Takes 528 bytes total with the bypass event to make it happen (bypass event hooks in where Celes's statuses are scrubbed clean).  Writing a custom event would take, like... 6 bytes of free event space, and however much space the ASM to empty the inventory requires?  Maybe 30 bytes total throughout the ROM?  That's way more efficient than what I posted.