Didn't look through those linked threads but you can not hold two real (in terms of OFP) weapons at once, so you would basicly make a weapon model that consists of two weapons (I hope you catch my drift)..
Now that is possible to be made look real enough with correct anims, but you still would have only one position where the bullet would fly from (OFP technical issue; there can not be two simultaneous 'bullet creating positions' utilised by the same weapon) so I don't really understand the benefit for all the trouble of making it
look like the unit is firing two weapons when it actually fires one..
Not to mention it's hollywood and arcdish, you can't hit anything with firing two handguns (unless you are Max Payne)