I get that for some people the entire point of playing an Origin story is to play that character as the opposite of how they're usually written, but that's not the case for everyone. I'm the kind of person who will play a completely linear game 2-3 times just to re-live the story and spend time with the characters and setting. I figured Origin would also give me extra content about specific characters that I wouldn't get by playing as a new character.
Also, I had been reading a lot of commentary about the game and characters well before I started playing; that's why I decided to give it a try in the first place. So... I wouldn't say I was going in completely blind.
There are some interesting devnotes about the Astarion/Karlach romance option, but I'm guessing this is not the place to post those.
Come to think of it... canonically, Astarion and Karlach grow to care a great deal about each other. She remains kind to him even when he's at his most sharp-tongued. If your Tav is romancing both of them, he'll tell you to break things off with him to spare her feelings (emotional growth, we love to see it!). So... even if they're not romancing each other, why not have the option to have Tav suggest he accompany her to Avernus? Obviously, this would be a spawn-only option, because 1. he'd still have to worry about sunlight 2. Karlach wouldn't agree to spend years with Ascended Astarion 3. Spawn!Astarion is the version who chose to break the cycle of abuse rather than perpetuating it, and begins to approve of good character actions. This could well be another step in his character arc... plus, no radiant damage, no running water, and an excuse to shed rivers of demon blood.
