Honestly, Terra getting amnesia by losing all her 2yr memories of being taken would be a more refreshing take. She wouldn't die so Brion could succeed in saving his sister. She wouldn't die like she did in comics or the movie. But it'd still be a tragic thing because she'd have lost her memories and if she got them back she'd be a criminal. Brion would never look at his sister the same way again and she would never know or understand why. That or she loses it all and Brion won't have her at all.
It would be vastly different. Brion having to deal with that, would be a powerful thing because it would force him to confront all the shit that has gone down because of how people view things. He’d have to confront not only his own bad behavior but maybe his parents or his twins or his uncles. Given what Sensei said to Brion, I have a feeling that Tera probably feels a bit bitter about something and maybe thinks he and Gregor aren’t paying her enough attention. Losing her memories would fit in well, and still it would play into the idea of the Judas contract. I like this idea, I hope it’s an option.