Highlight the political motives behind Daenerys’ turn
Daenerys’ genocidal run is depicted as being borne purely of her fury and despair, and that’s definitely a big part of it. But I think there are other dimensions we could explore.
For instance, before the attack on the city, Varys decides that it’s Jon Snow who should be on the Iron Throne rather than Daenerys. He drafts a bunch of letters, presumably intending to send them to the Great Lords of Westeros, but Daenerys finds him out and executes him before he can act on his plans.
…I think. Frankly, the show isn’t terribly clear on what exactly Varys is planning or whether he succeeds. Does he send those letters off, or does Tyrion rat him out before he can follow through? I genuinely don’t know, and that’s a problem.
We need to clean this up. My idea is that, before Varys is executed, we establish that he does manage to get ravens off to every corner of the continent, meaning that everyone will soon know that there’s another possible candidate for the Iron Throne. Famously, Jon Snow does not want the job, but that won’t stop Daenerys from taking this as a threat to the legitimacy of her rule.
And now we come to the moment of truth. With these events in place, Dany’s attack on the people of King’s Landing is an expression of her rage and pain, but there’s also a political dimension to it. She’s sending a signal to every great lord in Westeros: “This is what will happen to you if you back Jon Snow’s claim to the Iron Throne over mine, so think twice.”
I think this reading is possible to make even without these changes, but you have to dig really deep. Tidying up the timeline with Varys would bring it to the surface.