...but who else would you like to see as an option in the future?
This is hard to answer because, in some ways, everyone. Even if it's not full cut scenes, it would feel more immersive to be able to develop something with random characters that you spent enough time around.
But I recognize that's entirely unrealistic, and it's too big of an ask.
All that aside, other than Halsin, a few of the NPCs who stand out (in my opinion) are:
1. Arka. Develop a relationship with her. Help her get over the loss of her brother.
2. Nettie, I could understand someone wanting to romance her.
3. Alfira, the bard tiefling. I don't like the idea of romancing her (that close-up of her animal-like tail grosses me out), but I know there's interest from other players.
4. Lakrissa, I agree, there seems to be some subtle chemistry there between her and Tav.
5. Rolan, I can't imagine why someone would want to romance him, but I do think the scenes would be funny.
6. Kagha, would make for an interesting romance option.
7. Apikusis, the druid with the bird, the one who says, "The bird needs to know. You do not."
8. Aradin, Remira, or Barth... any of those would make for an interesting connection, even if only briefly.
9. Novice Brynna or Andrick... both of these would be strange options, but I could see it working in the story.
10. Mayrina. Another strange option, but it's a choice that would carry weight in the story.
11. Gandrel. Imagine Astarion's anger, or the humor if Astarion were the one doing the seducing.
12. Roah Moonglow, or Dammon, or Arron... obviously trying to get close for the discount.
13. Zevlor. Poor fella, all overworked. He could use a date.