Regarding morality and alignment, it would depend on how the whole system is implemented, I do agree with you that if the effect is more like true resurection then morally that's gonna be fine, but again, if the system is couched in terms of indentured servitude or if redemption isn't presented as an upside, then it could still very easily come off as a pretty evil thing to use. It might not, but it's not a guarantee.
Also if the flavour were to be that Withers is specifically reviving people who were on the nautiloid, that works since they could reasonably be anybody and so we wouldn't be limited in who we create. However I don't think ressurecting other NPCs who were involved in the story in this manner is a great idea. It'd be a lot of work for Larian to have to square the circle of their past and possibly future involvement in the game with them being potentiallybound to serve us as companions. And if Larian didn't do that, then they'd end up just as empty vessels, which probably would remove the appeal of bringing them back in the first place.
