So this is just me shooting an idea but an exotic that is actually 2 sidearms and instead of being able to ADS you fire the left hand weapon (could be reversed on PC to keep everything simple to remember were left click is left gun, and right click is right gun) anyways as for the perks you could have it be A: 1 gun primes then the other does extra damage to primed enemies that primes them for the other gun to do more increased damage B: be 2 different elements where the 1 weapon is the set element and the other you can change in the menu like the scope for the Queenbreaker or have it setup like the Borealis where you can change on the fly. or C: some other perk that you could think of that would benefit from Duel wielding. So ya those are just some thoughts that came to mind.