I really don't know anything about animation beyond that of a one month maya student, but would it really be that hard to animate dualies? There's really only one way to dual wield and fire a gun: both arms out, ridiculous looking or not or not.
As far as fairness goes, I'm not sure an accuracy penalty would even be necessary. As far as I could tell, it didn't affect your accuracy in the original, and as far as overpowered weapons goes, just define the off hand gun as a separate weapon and then tier the dualies accordingly like most games do.
On a side note, less than half accuracy for the klobb? You'd be more likely to shoot yourself, which at that point probably wouldn't be a terrible option.