Dual-wielding in Fallout's requires:
1. An off-hand gun raised animation
2. Trivial scripting
It's easy. We've known it's easy from GECK Day 1 thanks to the FireWeapon command. The hard part is getting the animation, and the fact that you can't make weapons off-hand on the fly without a lot more FOSE functions and plugins, so you'd be stuck dual-wielding the default game weapons (unless you wanted to spend aaages making compatibility patches and off-hand versions of every overhaul mod's weapons ever).
As I have mentioned in the past I ALWAYS add personal DW mods into the games I mod I did it for Morrowind, Oblivion and even FO3.
All that is required for FO3 DW is some animations and a very small bit of scripting to do it in a manner that is basically pre-setup.
1) I set up Benchs with scripts that would read your inventory for the presence of certain weapons like two Laser Pistols and it would take them and give you back a new weapon Duel Laser Pistols.
2) Created a new set of attack anims (I used Attack6-8 because they never got used in the original FO3).
3) Then I created some new HandGrip anims that controlled the left hand along with the attacks.
4) From there I had to create one SI that controlled the left hand resetting to the proper position after playing the Reload anims (I used the basic ones bacause I did not feel like messing with reload SI's).
5) Then I altered the original game weapon.nifs to be DW weapons -> this process required me to just static skin two weapons to the hand bones (because this is the ONLY way to get the offhand weapon to show itself in 1st person since armor addons and backpacks are culled from that view).
Ultimately it worked as a decent PoC, since both weapons were always identical weapons I did not have to bother converting AC to Dmg like I did for Oblivion and Morrowind but the weapons also did not animate because they were rigged -> and I am not about to alter the skeleton.nif to add an animatable version of every weapons nodes into it.
Thats pretty much as far as I took it before I had to stop modding because of work, so if anyone was interested its actually very easy and with some time and another way to make the offhander to actually show itself in first person it could be taken past this, but as is its very unusable in its current state with exception to being used for melee weapons it works perfectly for them.
Isnt there an excellent animator modding for fallout? his mods would be a lot more popular IMHO if it were compatible with EVE
Being a good animator does not make mods popular !... Of course I rarely waste my time serving what the public wants either so I guess it works out in the end.