I love speculation like this.
Writing in extremes, as it were. It's a healthy way to approach a subject. If you turn down the darkest of paths and play out how bad things could be, it makes reigning it back for the final draft feel more natural. Keeping in mind how dark it could be lets you create moments that pull the character back toward the light.
I really doubt all of their lives would turn out so dark as you imagine but for the influence of a single, heart-broken young man, but it is entertaining to wonder how many of them would have stayed along a dark road like the ones you described. Especially the bit about Rin.
The way I'm writing my Reunion fic, I've taken some influence from such ideas. Mine's a bit more optimistic, though.
