I know that there have been discussions before about dual wielding before and how it was shot down (heh) as it was unrealistic and would just end up wasting ammo except at point-blank ranges, but all their arguments were based around a normal human. I haven’t actually seen anybody making the bionics argument.
As it is now, we have these bionics in-game:
Targeting System
Cerebral Booster
Wired Reflexes
Muscle Augmentation
With these installed, you would have a survivor that can figure out the range of a target on sight, sync your arms to track them, use their coprocessors to keep track of multiple operations at once (aiming at two different targets), have the reflexes to switch their focus from target to target rapidly, and improved muscles that would help with managing the recoil. Things that are in-game with real-life counterparts should be realistic, yes, but we must also keep in mind how they would interact with the unrealistic, fictional things that we have.
Of course, it would be a waste of time to add such a code-intense feature if the requirement was getting a bunch of rare, end-game bionics that most players likely will never get all of in one character. So my thinking was to make it just require the targeting system or cerebral booster for barebones usage (that is, shooting at two targets in one turn), but with a penalty to accuracy and recoil.
Installing the other bionic out of these two base ones, plus the wired reflexes, would reduce the accuracy penalty per bionic installed. With all three, bionic-assisted dual wielding would be just as accurate as how you would normally shoot.
As for recoil, muscle augmentation (and possibly the Recoil Compensator CBM as detailed below) would reduce it, but never to the point to where recoil would be equivalent to firing your guns normally.
Functionally, the interface would be pretty much the same as normal: you would hit the f key to fire your guns at a target, and after picking your first target to fire at, you would then pick a second one with your second gun. After that, both shots are executed at once (or the first shot takes no time and the second one does) or something like that. You would be able to [a]im carefully if you have the cerebral boosters installed, but not fire a [p]recise shot with it without having all three accuracy bionics. (Or possibly make precise shots flat-out impossible with this)
Also, mutations. I can see some of the slime mutations (distributed neurology and distributed senses, mainly) as being compatible with dual-wielding.
In addition, maybe add a Recoil Compensator CBM that goes in the arm/hand slots and does exactly what it says on the tin, but also give a bonus to dual wielding? And possibly fold dual wielding in with Bionic Combatives. It fits the theme, at least.