Loved reading your thoughts on Edward and Jasper's relationship. Especially the last part with what happens after BD. How do you imagine the situation would resolve? Will Aro get his hands on Alice eventually?
Thank you so much for asking this! I've been thinking about it a lot, since I wrote my Edward and Jasper post (I'm glad you liked that one :-) ).
Realistically, I don't seen this ending well for my OTP. However, this is unacceptable so here's a less realistic but better ending headcanon I came up with:
Alice and Jasper tried to stay with the Cullens for as long as possible, while secretly discussing their options. However, once Alice's visions of Aro making a move became more frequent and turned violent for the other Cullens as well, they decided that it was time to leave the family and cut all ties. The Cullen lifestyle just made them too easy to find and this was the only way to keep the others out of it.
Alice's initial plan was to find a non-confrontational and non-violent approach. She considered travelling as nomads and hiding from the Volturi for as long as possible, but her visions told her that wouldn't last for long. Next, she thought about talking to Aro and finding acceptable terms (like e.g. a limited time of service, letting Jasper join as well, guaranteeing their dietary needs etc.). Unfortunately, she didn't see that work out for them either and thus agreed to Jasper's more extreme plan, when they left the Cullens.
Jasper, who had been plotting this since Alice's trip to Volterra in New Moon, had briefly considered a confrontational approach. They wouldn't be able to attack the Volturi head-on by themselves, but maybe he could get the Romanians or Egyptians to make a move? However, that approach was eventually discarded for what he considered to be their best strategy: Finding a replacement to offer to Aro in Alice's stead.
So, when they left the Cullens, Alice and Jasper started to scour the earth for a vampire with similar talents to Alice's. When that didn't turn up any promising leads in the first weeks, Jasper quickly branched out to considering humans who displayed signs of clairvoyance as well. (Imagine Jasper threatening con-men and -women into admitting they don't actually see the future—the image is glorious). Alice wasn't entirely on board with the plan but by this point the threat of losing Jasper and the Cullens forever was very real which made her desperate enough to accept the selfish act of offering someone else in her stead.
The pair reconnected with some of the Cullens after Alice accidentally killed the first promising human in an attempt to turn them. Jasper's plan was to guilt Edward into helping them, since he was in his mind the one responsible for this mess in the first place, but he underestimated Edwards aversion to condemning humans to their existence. Fortunately, Bella, who overheard their argument, didn't share Edward's reservations and was all game—she really wanted her best friend back. So they went ahead behind Edward and the other Cullens' backs, keeping their ploy a secret using Bella's gift. And on the fourth attempt, they stoke out lucky.
Bella turned a human who manifested a similar gift to Alices. He was able to see the future of anyone he touched (similar to Aro's gift). While this made his talent slightly less powerful than Alice's in terms of who he could see, his visions were more precise in terms of knowing time and place, and he could also see very clearly whose future was entangled with that person's, knowing exactly how these people's actions might alter the current course. Jasper decided that this had to be good enough, so Alice and him contacted Aro for the exchange. He, of course, acted all surprised and denied that he would have ever made Alice join unwillingly, but eventually accepted the gift, enabling Alice and Jasper to resume their life with the Cullens.
However, knowing that they sacrificed other people's lives for their happiness changed Alice and Jasper forever and, once they returned and Bella's shield was no longer enough to keep their secret, the entire Cullen family wasn't the same again. Esme, Rosalie, Emmett, and obviously Bella were okay with their actions and welcomed them back, but Edward and Carlisle seriously struggled with what had occured for a long time.
That's it! Kudos go out to my awesome friend / writing wife @theunexpectedness for making this headcanon even more awesome by suggesting Bella's role in it (I initially had Jasper pegged to be able to convince Edward). You're the best!











