Re-rewriting the Astartes Codex (chapter supplements). Rogue Trader gave me the bug. It doesn't help that I got to game-stopping design idiocy-induced bug.
Anyways, was actually thinking about the Furioso Dreadnought, and wondered why it had it's own special-purpose ranged weapon. The whole point of Furioso Dreadnoughts is to put an armoured box of fuck-you two feet from the enemy's face. And the answer is because the Codex limits Dreadnoughts simple fist weapons, which is part of the same bullshit that GW pulled with the whole Codex. I mean, here are these super-powerful, super-rare, ultra-space-knights, who have the Emperor-given authority to tell the High Lords of Terra to go fuck themselves, and then take the biggest badass, and...
completely limit his weapon's layout.
Like, we venerate you brother, for all you have given to the chapter, but Guilliman says you're not allowed to use swords anymore.
One of the things I fixed was offering Dreadnoughts a much larger variety of melee weapons, that have a more disparate range of effects.
This means that a model can carry two melee weapons without losing much in the terms of fuck you combat power.
But, there's no reason to shitcan the unique gun. So, the answer was just to give it to regular Blood Angels Dreadnoughts, like Inferno Pistols and Hand Flamers are added to their Pistol lists.