I dont know if its possible, but I would like a mod where your weapon slots is restricted to just one. Maybe that would give the combat more depth if you combine it with a 3x durability mod. SInce you can increase the count in game anyway I would think its just a variable to change but i know nothing about modding this game. If anyone feels up for the challenge go ahead. Cheers.
If you're playing on CEMU you can use this memory editor (can't post links yet sorry): reddit -> r/breathofthewow/
Then simply load up a save, run the editor (with admin rights), click Scan Memory, wait a moment till it scans, go to the Slots tab, type 1 in the Weapon Slots field and press Update.
As for the actual mod - I don't think it's actually as easy as replacing a single value in the files, as some parts of the game are hardcoded into the executable, and I think here it's really the case because of Korok's ability to expand the weapon inventory (which needs to be saved and stuff)