When you talk about dual-wielding and two-handing there's also the question of paired weapons coming up, really.
From dual tonfas and dual daggers to dual pistols in theory you can have weapons that, while taking up two hands, actually represent two one-handed weapons that are exclusively used as a pair.
The question there is if people find it immersion breaking that they can't be seperated, e.g. you can't just use one of the pistols instead. The issue in theory exists with things like shoes or gloves, where generally people won't care that you have a pair of shoes that is stuck as a pair and you can't just wear one shoe, but when it comes to items that are more 'used' than 'worn', like weapons, opinions might differ.
If a review of two-handed economy is done I'd say it would also be worth looking at that kind of 'dual-wielding', since it adds another point to balance things out against in terms of, say, a damage vs. accuracy trade-off or what you can 'get' for sacrificing another hand.