If the Lannisters had crowned Aegon... hypothetical scenario

[AegonTargaryen]

We've seen tons of "what if Rhaegar had married Cersei" threads, but let's approach this one a little more concretely. Let's assume events unfold the same way with the exception of Rhaegar being married to Cersei, and Aegon and Rhaenys being Cersei's kids.

Seeing as Rhaegar has run off with Lyanna, I don't think Tywin is particularly eager to support his cause. I mean that's quite an insult to the honor of house Lannister. Instead, Tywin sends a token force, or hides in Casterly Rock. Perhaps he even secretly negotiates with the rebels. Nonetheless, he still wishes to see his grandson Aegon on the throne. Fast forward to after the trident, the Lannisters have entered the city, and Jaime has just stabbed king Aerys. What's next?

I think at this point Jaime declares his infant nephew Aegon king of Westeros, and Tywin as his guardian and lord regent of the realm for the duration of Aegon's minority. Lannister bannermen rush to Cersei, Aegon, and Rhaenys, but instead of murdering them, they bring them safely into Tywin's custody.

As Ned approaches, Tywin has essentially made himself the de facto ruler of the seven kingdoms. What's the rebels' next move? Perhaps Tywin offers Rhaenys to Robb? What else can Tywin offer the kingdoms to return the king's peace and recognize Aegon as king and Tywin as his protector for the foreseeable future? Or maybe the war rages on?

[otherbeef]

the rebels could have and probably should have crowned Aegon even with the events playing out as they did originally

[Maegor the Cuddly]

Let's see: I think Robert could've actually been okay with Aegon on the throne, as long as Lyanna wasn't dead. Yes, he was angry at the Targs, but I don't think he anger was truly at the level of hatred we see him with later in the books until Lyanna died. If Tywin made some concessions, maybe even promising to kill Rhaegar and give Lyanna back to Robert, Robert would have wound up bending the knee.

Ned's distrust of Lannisters began when he found Jaime on the throne, but if he goes to see a Targaryen child, surrounded by Lannister swords to protect him from the rebels, maybe he would have been willing to negotiate with Tywin. Hoster Tully appeared as though he was willing to go along with Ned due to the familial ties between the two, and Jon Arryn seemed to favor erring on the side of caution. Those three would have been more than enough to get Robert to calm down, and bend the knee to Aegon.

Maybe here's the way he gets peace.

Appease Ned Stark - Offer to chase after Rhaegar and Lyanna, get his sister back. Offer Brandon and Rickard's armor for burial.

Appease Hoster Tully - Some holdfasts, and perhaps a Small Council Position.

Appease Jon Arryn - Not much to offer him, besides maybe coin and a Small Council position.

Appease Robert Baratheon - Swear by the Seven to hunt down Rhaegar and execute him, and return Lyanna to him.

But then, The Reach and Dorne probably would not have been happy, nor would have the various Crownland Lords.

Appease Mace Tyrell - Offer him some holdfasts from the Crownlands, and offer Rhaenys to be married to Willas Tyrell.

Appease Doran Martell - Give the Dornish some extra autonomy, a la Jon Arryn, and maybe a marriage between Elia and a Lannister cousin?

Appease Various Crownland Lords: Offer up holdfasts closer and closer to KL, and give the vengeful vassals some extra land from the more pacific ones. Requires major reshuffle, not entirely necessary as the Crownlands would need to unite to be a threat.

[Djinn]

If Aegon is Tywin's grandson, no way he let the rebellion escale to the point of declaring Robert their king without interference. When Mace chases Robert of the South, Tywin hunts him down. Then, he presents terms.

If this is before the Trident, the whole war would have serious lion action. If after, Tywin would still try to secure the rights of his grandchildren.