It feels like an attempt to straddle the two kinds of RPG's we've seen over the last decade;
On the one side you've got Mass Effect and the Witcher series, where you have a main character that very much has their own identity and story.
On the other you've got Baldurs Gate 1/2, Dragon Age 1, where you're character is a blank slate to be filled in.
I think both styles of games can be enjoyable, but I do recognise you're making some pretty big compromises in story telling to put BOTH into the same game.
I think they're spreading themselves a little thin to be honest. It's going to be hard to try and make easy of the playthroughs unique and interesting.
They tried to some extent with DoS2, with each character having a few unique dialogue options and quest events that set them apart, but I never felt much desire to play the game from their point of view. In fact, a lot of the personality and character was often stripped away when the player took control of the characters.
I understand what they're trying to achieve, but yeah.. I think it's a very ambitious feature and difficult to do well without spreading yourself thin.