We are playing hypothetical games now?
The most i would be concerned about story is, how can a lvl 1(!) cleric of shar have such an important mission that they took her memory away until a specific spot? She won't get any levels back(assuming she lost levels as well, which she didn't).
How do you even trust a nobody to do that? There is only one answer, she's not a nobody.
There is something about all the npcs-origin characters, something that overshadows your own custom origin character, which is actually a nobody.
So you're asking me to be excited about playing a game, where i know for example Astarion will always be a better rogue than you(bite-buff), Where Gale is gonna be a better Wizard than you, etc etc.
So there is your one thing that makes not excited for example. Origin characters, and protagonists as well, in a game where there used to be only one protagonist.
There are several other problems as well. It doesn't mean the story is gonna be bad. But the origin system alone means one thing. If origin characters can be protagonists as well, they can live through a protagonist's eyes. Which means they will always have something more from their backrounds compared to Tav. I eagerly await to see how are they going to avoid the same problem they created themselves in DOS2.