I'm not even sure where to start with this.
I disagree with having npcs in the store prior to exposition. Not just the EP store being open, but full on exposition.
There are too many things we don't know. How much players will regret their overpopulated settlements, what exact npcs towns already have, whether we actually care about certain crafts at this stage or if we just like the idea of them and the reality will be much different than expected.
There are about 0 merits to offering npcs for purchase this early in development and more reasons to Not do it than I can think of here on the spot.
(side note, the like/dislike way of voting is difficult because some people will upvote this post just because they like the discussion and not necessarily because they care one way or the other)
Edit: Just to clarify my personal stance. I'm not against the purchase of NPCs during Exposition I just don't think they should make an appearance prior to that in development.