Lemme see… was it Incursion roguelike that had a solid ground for main and off-hand?
Altough really inconvenient for a typical RL player IMHO, it most surely is a good basis to reconsider realism considering manipulating different objects when it comes to RL games. Let’s assume it applies to CataDDA:
Besides typical slots for clothing and armor, you can do as much damage in one round as both your arms can manage. A proficient dual-wielder could fire up two burts from each uzi, attempt to hit single target with three bullets from each or aim a shot, but from only one weapon. When in melee, you can develop a style and try exotic stuff like shield-bashing and whatnot. All that, however, doesn’t solve the object manipulation issue.
So, what did the creator of Incursion do, exactly… He created an extra slot which he named (something like) in-air which lets you access objects in containers, on the floor and more. It simply represents an object you’re holding ATM and it doesn’t allow you to do much more than chewing a bubblegum until you finish the job. So, let’s imagine a mom (yes, a typical mom-with-kid) holding her daughter in main hand (it’s an arm, moreso) and wielding a plastic shopping bag in off-hand. The pig-tailed poopbag drops a toy on the ground, so she must grab the kid tightly, put her hand through the bag handles, crouch and pick up the damned toy, get up put the toy into her daughter’s hands and finally - get hold of the shopping bag again. The in-air object, as you can see, made her completely prone and unable to do anything else until the action was finished, since she was dual-wielding!
Your typical CataDDA character isn’t much different; he/she could wield a crowbar in main, and some swordlike item in off-hand since a crate needed prying. Let’s say there was a chocolate inside, so he/she decided to eat it. Even though the character was just eating, the chocolate was treated as an in-air object since it had to be picked up before accessing. After breaking the seal, the character’s elbow presses the crowbar against the chest, picking the object up. (E)at the “in-air” chocolate by picking it up with main hand so you can rip the wrapper with your teeth, and you’re left with the wrapper itself afterwards. You can then discard the in-air object which allows you to handle the crowbar and, for the sake of it, pry yet another thing in this ep. of Chocolate Quest.
Enough said, it is a feature of the inventory system. You can close the inventory to access other game aspects whilst there’s still that in-air object in your hands, but you can’t attempt any other action until you finish manipulating that object. With one-hand system currently in place you can always count on that other arm of yours to help you wrap things up swiftly. Guess the question really is about the complexity of dealing with items in CataDDA and other roguelike games.
The other “workaround” could guess the player character has a holster/sheath for every item, and perhaps a girdle of sorts for the shield items. It could treat the wielding items as temporarily strapped-on items, at the cost of realism.