I'm not sure that's possible, and if it is, it's beyond me. I'm still figuring out how to put custom items in without crashing the game, and naturally using two-handed weapons would prevent dual wielding. I don't know how we'd make the game recognise two-handed weapons and prevent double equipping (alternatively we could add a huge debuff?).

I was thinking more having it be a skill-tree that rewards useing wepons without things in the other hand. If the other hand is empty you get a boost, but if you have things in both you are clumbsy and such. It would be a blatant Warrior tree of course.

If we were working off of the initial dual-wield skill, I guess you could change whatever recognizes the second weapon to recognize shields and things as well, and then alter it from a buff to a debuff (penalizing anything more than one weapon) which would counterract positive buffs that were already passive in the skill tree. Basically if your skill tree had +1 to anything, equipping more than one slot would debuff -1. Add the clumsiness debuff and your first skill is all set. Then with every skill you add you just have to add equal or greater penalties based off it recognizing weapon/shield/orb/book in the second slot. Idk, someone else might have a better idea.

how

Well is there a reliable tutorial for editing the game, or are all of you just messing around and seeing what works? I wouldn't mind doing it myself, but without some kind of guide I don't think i'll have much success. And yes, I understand Google exists, I however like being pointed to where I need to go by people who know what their talking about instead of a computer.

I mean... Im currently dual wielding halberds... I guess it doesnt matter...