Idk how many of you are fans of Lucifer, but those you who are may remember, Maze asking god for a soul, but God says he can't. Later on it is discovered Maze was able to grow a soul.  This idea always stood out to me because of all the things it suggest about good and evil. But before I jump into a fan girl rant  about Lucifer I'll get to the point, which is what if souls were like that in  the BTVS verse. 

So here is the challenge:

In BTVS and Angel: Souls aren't things that can be given or taken away at a drop of a hat. A soul is something that develops over time.    How does this change things?

(optional) Possible Idea:

Spike always had a soul

Buffy's soul slowly withers in season 6 

Watchers lied about vampires/demons not having souls to make them easier for slayers to kill

(if you want to go full Lucifer) Angel's curse is just the gypsies making a deal with the devil to bring his hell loop to earth until he forgives himself.