Definitely Upper City DLC and thats where Astarions story lies, definitely playable Goblins.
Waterdeep could be another DLC idea.
What I wouldn't mind is a dark urge pre story DLC and the setting up of the main story It would be interesting though You'll have to accept that Orin ruining your head as the final scene of it.
* Crown of Karsus being stolen from Mephistopheles the dead 3s original set up.
* Tadpole alteration in more detail
*plenty more Gortash (I can listen to Jason Issacs all day )
Not Pre Story DLC : Cure for Vampirism
Cure For Wyll's Devil Form
Cure for Karlach thats not Avernus or death/mindflayer (upper city ?)
Spawn survival and reeducation in the Under Dark
