There's been some more discussion on my alternate-history message-board about the alternate A Song of Ice and Fire timeline beginning with King Robert Baratheon dying in the last days of the Greyjoy Rebellion after he and Ned Stark kill "King" Balon Greyjoy and his burly brother Victarion. Here is some of the earlier discussion I've posted, and what's coming is what came afterward.
*The Mad King Aerys II had caches of wildfire left all over King's Landing and Jaime Lannister killed him when he tried to set them off. Possible major stashes could include the Red Keep where the king and his minions would have easy access to them, the Dragonpit for maximum casualties, and the Great Sept of Baelor to give the Seven the finger for not helping Aerys. Euron's raid on King's Landing thus far seems to consist of an attack on the Great Sept where Cersei is captured and another attack on the Red Keep. Both are set on fire after being plundered. If even some of the wildfire goes off, we might have something akin to the Great Fire of London (the first or second) or the fire in Rome under Nero, which could kill tens of thousands if not hundreds of thousands of people. Depending on how much damage is done, it might be necessary to move the capital to Dragonstone or Storm's End while the city is rebuilt. Rebuilding the ruined city on top of a decade of partying by Robert might put the realm in the same kind of financial danger it was in canon, although Littlefinger supervised by Stannis Baratheon could no doubt supervise the raising of the needed funds without them going anywhere they shouldn't.
*Although Jaime Lannister will be Lord Paramount of the Iron Islands with Asha Greyjoy as his lady, other ruling houses will send younger sons to be lords where Ironborn families were wiped out entirely. The younger Stark boys could be given islands to rule, while Roose Bolton could send his murderous bastard there as well, possibly saving the life of his legitimate son.
(Considering how violent and sadistic Ramsay is, I can imagine him adopting Ironborn customs like taking "saltwives" and paying the "iron price" just to justify him raping and stealing.)
*The pro-Targaryen coalition (Euron Greyjoy, Khal Drogo, Viserys Targaryen, "Aegon," and Danaerys Targaryen) is going to run into trouble if Drogo dies per canon. In canon Viserys tried to sneak into Danaerys' room the night before her wedding to molest her and if she's widowed while he's still alive, he might try to claim her as his wife. Canonically both "Aegon" and Euron are interested in marrying her as well. If Danaerys has the dragons, she'll have the means of defending herself and choosing her own husband. I suggested that's one way to kill off Viserys is have him lay hands on Danaerys and then get incinerated by the dragons and/or chopped up by Danaerys' bloodriders. Alternatively, if Euron takes Dragonstone in the process of killing Stannis, he might kill Viserys in an effort to awaken dragons from the stone there. Viserys has royal blood and if he's still the nut-bag he was in canon, even ten years of brutal training in war and sorcery from Euron might not be enough to temper him.
(If we want Danaerys to name one of her dragons after her brother, maybe Euron gets wind that Viserys is going to go after her and then kills him? All she'd hear is that Euron killed Viserys and if Viserys was having some kind of drunken crazy episode like just before how he died in canon, she might not even blame him. She isn't angry at Drogo for "crowning" the obnoxious Viserys with molten gold, after all.)
*With only Joffrey and Myrcella born to Cersei, ostensibly fathered by King Robert, it might be harder to figure out that they're bastards born of incest. Most of Ned's children with his wife Catelyn look like their mother, but nobody claims she was secretly sleeping with her brother Edmure. Given how in this timeline Cersei gives birth to Euron's rape child and later (presumably) has children with her new husband Edmure, if those children tend to look Lannister (blonde hair, green eyes), people might not ever suspect anything. On the other hand, many of Robert's bastards have already been born and they're all dark-haired.
*The anti-Targaryen coalition could have problems of its own. With Stannis dead, if Joffrey and Myrcella are disinherited, this means Renly Baratheon is king. Renly tried to claim the crown in canon even though Stannis had the better legal claim, so him being an "Evil Uncle" to Joffrey and Myrcella might not be out of character. Ironically unless Ned has gotten proof, he might take Joffrey's side against Renly. And although Edmure is not head of House Tully until his father Hoster dies, he might be willing to defend his wife against any accusations directed at her. He was willing to stand by Roslin Frey in canon, after all, even though their wedding was a trap that killed his sister, nephew, and many of his political allies, and on at least one occasion he has been described as "soft of heart, soft of head." I'm imagining Edmure fleeing with Cersei to Tywin Lannister if it looks like his father is going to arrest Cersei for treason and incest, which could lead to a Tully civil war between father and son. Although Edmure doesn't really seem to be the sort to inspire a rising against Hoster, the possibility of having to fight Tywin might be...intimidating to some of the riverlords. In particular, I'm thinking of the slimy, opportunistic Walder Frey.
*Given how in this timeline Varys poisons Regent Jon Arryn soon after Hand of the King Stannis is killed in battle with Euron, he could easily send letters in Jon's name to Mace Tyrell, Renly, and Tywin telling them they're the new Hand of the King and they need to bring an army to King's Landing to protect it against another attack by Euron. If both of them show up at the city with armies, each will likely claim the other was planning a coup to take control of Joffrey. Each would have a credible reason to do so--Tywin is Joffery's grandfather and was Hand for 20 years to the Mad King Aerys II, while Mace has the very marriageable daughter Margaery he can marry to Joffrey to gain influence over the young king and Renly is King Robert's brother like Stannis was and has ample governing experience. All you'd need is a skirmish or someone getting poisoned and you could have a two-way or three-way battle right there. Alternatively, one or more of the leaders could back off to avoid a fight they can't win--and then start the fight on their own terms later.
*Meanwhile, the pro-Targaryen forces gather in Essos and Dragonstone and the Iron Fleet sails to liberate their ancient homeland from its occupiers.