Cersei and Lyanna switch places....What happens?

[Jon's Queen Consort]

Nothing like that. Tywin would had married Cersei to Rhaegar in public and once she was pregnant Elia and her children would die from a horrible disease or accident.

[The Frosted King]

I think you guys overestimate the power of Tywin Lannister vastly.

Jaime is squiring for Lord Crakehall and gets the news, you think he'll be stopped?

You honestly think if Rhaegar asked Cersei to run away with him and elope, promising to make her his golden queen, she'll start making demands at that very moment?

You must not have ever been with anyone who's nose was wide open for you.

Cersei will be missing just like Lyanna. The difference is the fallout.

[TimJames]

Rather than Brandon, it's Jaime who goes charging off to KL when Rhaegar absconds with Cersei(she wishes) before the Harrenhal tournament.

Jaime rushes to the capitol, calling for Rhaegar to come out and die. He's accompanied by Lyle Crakehall, Adam Marbrand and Listor Lefford.

What likely happens?

For this to make sense, I will assume that Brandon Stark is in the Kingsguard instead of Jamie.

With that in mind, I assume that instead of going himself to rescue Jamie (as Rickard did for Brandon in canon), Tywin Lannister will wait patiently and plot. He'll find the location of the Tower of Joy and send soldiers there.

If Cersei and Rhaegar eloped willingly, Tywin would pretend to press Rhaegar's claim on the Iron Throne. In reality, he will assassinate Rhaegar and Ageon and then sack Kings Landing. He will then marry Rhaegar's daughter to Jamie so as to ensure the Lannisters are kings once again.

[The Frosted King]

Again Tywin with the mystical power to have secret information plop into his lap.

Who tells Tywin where Rhaegar went? Or because he's Tywin, he'll just know?

[TimJames]

Again Tywin with the mystical power to have secret information plop into his lap.

Who tells Tywin where Rhaegar went? Or because he's Tywin, he'll just know?

Grand Maester Pycelle would probably tell Tywin in secret. Or someone else who is loyal to Tywin. The Red Wedding didn't just happen in the heat of the moment; Tywin has a spy network to find out what his enemies were doing.

[BRANDON GREYSTARK]

If Lyanna and Cercei switched places . They all will live happily ever after since Tywin wanted his golden daughter to marry Rhaegar and Cercei had already made arrangements for Jaime after her royal marriage . The question is would Jaime have done like Brandon ? Pre amputation Jaime I would believe him if he told me that rain was wet , he has a deep hatred of the Starks and the Baratheons . Now knowing what we know about Jaime . 1 He boasted he has been totally faithful to Cercei ,2 He tried to kill Bran when he discovered him the affair.(meaning he is willing to kill for her)3 He was complaining about all the men that Cercei was doing ...even moonboy .4 In ACOK Tyrion said of Lancel that Jaime would kill him if he found out . Jaime would have done everything Brandon did ,with the exception Tywin would not have gone to King's Landing without an army .

[devilish]

Rather than Brandon, it's Jaime who goes charging off to KL when Rhaegar absconds with Cersei(she wishes) before the Harrenhal tournament.

Jaime rushes to the capitol, calling for Rhaegar to come out and die. He's accompanied by Lyle Crakehall, Adam Marbrand and Listor Lefford.

What likely happens?

Well the story would be different though.

a- Cersei wouldn't escape with Rhaegar willingly. Her ego wont allow her to be second best to Elia Martell (Elia's children would be heir to the throne and not Cersei) + she wont cross her father by doing so. In few words Rhaegar would have to abduct her

b- Jamie wont rush to KL because he's already there as Kingsguard. Unlike Brandon he knows that Aerys is as mad as a horse and he wouldnt dare crossing him. Aerys on the other hand won't treat Jamie the way he treated Brandon. He's too scared off from Tywin to do so (he threatened Doran with Elia but he never threatened Tywin with Jamie and allowed him to stay out of the civil war). If he arrests Jamie, Tywin will find ways to have him escape. If not, Jamie will find the right time to cut Aerys into pieces and then escape. Tywin had served as hand of the king for years and knew that Aerys was mad. Surely he had made enough friends in KL to get Jamie out alive and assassinate Aerys if needs be.

c- Once Jamie is at the Westerlands Tywin would call the arms. The Tyrells would join him (historical ties + Jamie would be offered to Margaery). A lot will depend on Arryn. The man is as straight as an arrow and has a soft spot towards the blondies so he will probably join the Lannisters because that's the right thing to do. (Rhaegar kidnapping a lord's daughter is uncountable). He'll probably drag the Starks and the Baratheons into it with the former being granted independence or have Cersei marrying Eddard if she's found alive. The war will end up quickly.

[Pikachu101]

You honestly think if Rhaegar asked Cersei to run away with him and elope, promising to make her his golden queen, she'll start making demands at that very moment?

You must not have ever been with anyone who's nose was wide open for you.

I do because Targaryen mistresses were a norm so families will be teaching their daughters how to react to such a situation so that their honour won't be tarnished. Lyanna was wild and impetuous, Cersei isn't because running off with Rhaegar would have been social suicide.