John Woo, Fallout-style: Hell yes...
I think it's a great idea.
Howabout anyone can dual-wield pistols, but also introduce a trait.
something like this:
Ambidextrious
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You are skilled in the use of both your hands
this would be like the one-hander skill, but increase accuracy with two handed weapons (the big guns skill) and give a bonus to accuracy when wielding two weapons at once.
you could dual-wield any small gun, melee weapon, unarmed weapon, with decreasing accuracy the larger the weapon and the greater the recoil: two pistols, barely nothing, two smgs, moderate, two shotguns/rifles, heavy
two knives, barely nothing, two clubs, moderate, two spears, heavy, etc.
add an extra ap cost and another point requirement for strength, and double the reload ap cost. then take away aimed shots, and you basicly have a burst attack for the pistol.
to solve the problem of say, a 14mm and a magnum, you would only be able to use two weapons of the same type, as in Devastation. or at least the Devestation MP Demo. i.e., a set of dual magnums, or a set of dual 14mm's.
this would make small guns a skill usable the whole game; dual-wielding two gauss pistols or G11's would be pretty badass.
and yes, it would make pistols overpowered; but take into account the short range pistols have; you would have to get close enough to the raider with the ak47 to actually shoot at him accurately while he could lay down several bursts.
and as for a desert eagle doing more damage than a hunting rifle...a desert eagle can load hollowpoint rounds, which mushroom on impact (flatten out: they basicly end up leaving a small hole at impact and a large hole at exit) while .223 or 7.62mm rounds(military issue) depicted in fallout are brass rounds, which usually stay the same size from impact to exit, and have been used in virtually all anti-infantry(military) weapons since the geneva accords. which is why, in fallout tactics, the 7.62 had average penetration and damage, and why 9mm hollowpoint had less than average penetration but increased damage.
so think of it this way; two pistols= a shotgun with two large, accurate pellets and a bigger magazine. Think Old West. It adds to the close-range gun combat, nothing else.
and perhaps at 200% in small guns with say 8 perception(to notice two targets) and 8 agility(to sucessfully aim at two targets), you could pick a perk that allows you to shoot two people at a time, if you so choose, or make called shots. you'd be a close range killing machine: but by the time you got there, you'd need to be.
instead of staying at 50 yards or so away with the sniper rifle, you could sneak in with a couple glocks and clear the place out, matrix style, with the already low ap cost, and being at close range. it'd be somewhere between the slayer and sniper perk; but it would also mean that the sniper perk would have to be changed to a min. range or certain weapons.
it would take an extra bit of balancing and beta testing, and it would definitely add some new style and dimension to the game, and i personally wouldn't mind that.