I was thinking about the theory I've seen that Shadowheart was a Selunite brainwashed to go on a suicide mission for Shar, and how she mentions her memories will be returned to her in BG, but I might have understood it incorrectly. I was assuming she would have been a Selunite recently brainwashed to go on this mission but now I'm wondering if the mostly nice person we know from the EA is a result of all her memories as a Shar cultist being taken, leaving behind the person she was before being broken into Shar worship, a personality potentially many years old, many years of very unpleasant things.
This would set up the potential for a drastic character shift later in the story, we'll potentially be dealing with a very different person, possibly one more upfront with their alignment. I'm not sure how well this kind of twist could play out, especially with SH as a potential PC. I guess this was a bit more obvious to most people, and I don't know if the data-miners have weighed in.
I love the idea, especially with Shadowheart as a companion. To imagine having a player character falling in love with her and then wham! The rug is pulled out from under the feet, and Shadowheart completely changes into a full blown evil cleric of Shar. Wow, that would be brilliant and emotionally powerful.
But... you bring up a good point about Shadowheart as a player character option. Doing something like that would be really difficult. As it stands, I think there'll be little reveals all the way to Baldur's Gate, like the moment in the village with the schoolbook and the hopscotch and the abandoned helmet. Small reminders of who she is, so as a player character, the reveal in the city after she gets her memory back isn't so jarring to the system. Because ultimately, the player will have to decide how to play her personality when the dust settles.
As such, I lean toward thinking she'll be troubled, but mostly good at heart, if only because it will be more palatable to most players. If I were to hazard a guess, I would say that she's probably been blackmailed into her current quest somehow.
