I have suggestion for a Halsin quest.
Tied into his dislike of the city, and a lot of the banter and conversations we get with him during the game about the refugees and many orphans, I think a quest leading up to how his romance ending is would be good. It would already be supported by existing dialogue.
The quest could be aiding some of the refugees, who are being scammed and used. Specifically, we could have a quest, where orphans are being used or possibly sold as slave by a part of Gortash organisation (since slavery is already an established form of business for him).
Halsin's quest could be investigate these disappearances that no one else bothers to look into. Additionally find orphans who are sick and needs to be cared for.
Halsin's comment with "Daddy Halsin they call me" is extremely cute, but it comes out of nowhere. A quest line, where he and Tav actually establishes a relationship with the orphans (like the tiefling boy who saw his parents killed), Yenna, and the tiefling children all the way back from the grove, who start to establish this.
The quest would further cement all the conversation and banter he already has, but would also open up for dialogue into his past: How he lost his family, and the infamous drow dialogue could be tied this without it being gated behind the drow twins.
It would bring in some continuity to his character.
