What if there was a perk to let you use two hand cannons at once? Both weapons would need to have it, and it would greatly reduce stability and reload. One notable pair in my mind is TDYK and TDYD, just because of the names, but you could combine any two with the perk.
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Or add a fourth character slot and the Fallen as a class after HoW. As you level up you go from Dreg to Vandal to Captain. Once you become a Captain you can either dual wield ARs, SRs, and PRs or quad wield HCs. Four Fatebringers at the same time....