I've been toying with the idea of portraying the Gully Dwarves of Xak Tsaroth as a people who took to this area as a refuge... and the ruins have been destroying them and reducing their mental capacity through environmental contamination ever since. It's not just a mental deteriotation - physical, too. There are no old "Aghar".
And there are records in Dwarven which explain how they first came to Xak Tsaroth in the wake of the cataclysm, seeking shelter. Very few of the existing Aghar are able to read them now -- but the PCs could. Not only will these records lead them to the existence of the secret passage into Khisanth's lair, but it should clue the PCs in to the cause of their misery.
The ruins provide the key to unravelling their "curse". They are victims of lead poisoning as well as perhaps some other biological contaminant. The pipes the PCs can navigate are all lined with lead. It's everwhere. So is the mould. Or perhpas, the mushrooms the Aghar eat are an environmental concentrator of this lead contaminant.
It is affecting not just the Aghar, but other animal life in the ruins that eat those fungi.
And that is something that the PCs can discover and then at least act to prevent - and ultimately, cure. Even the destruction of Xak Tsaroth itself will provide the children of the Aghar born in the wake of that event longterm hope - as those will escape the cycle.
tl;dr: Gully Dwarves as victims who can be saved and redeemed is a worthwhile quest objective. Actually curing the Aghar of their poisoning and restoring their dignity could be revisited later as the key to securing the aid of Thorbardin -- and the step towards re-uniting the many Dwarven clans. The clerical powers of the new human priests should be just high enough to begin that process of curing disease and neutralizing the poison by the time DL3 & DL4 play out. The fate of the Aghar is therefore ultimately tied to the fate of the refugees rescued from Pax Tharkas - and there were many Aghar in Pax Tharkasmoved to work its mines by the Dragon Army.
Point is: there should be 100-200 Aghar with the refugees outside of Thorbardin. Compassion for the Aghar will beget compassion from the Mountain Dwarves. In this way, you can have your cake and eat it, too, when it comes to the Gully Dwarves; the re-write is modest. It's how they are presented and how their fate is ultimately treated which is the key to updating and meeting the moral charge of "cruel ableism".
