To what degree would this be viable? I've looked around the internets a bit, but I haven't found a particularly good explanation to how it would work.

It's 1950's pop science. It isn't supposed to make sense.

Well played.

But I'm wondering (for the sake of keeping lore intact if I make a ghoul character for an RP) whether or not a ghoul could have their arm reattach itself after being separated from the body, or if a 9mm to the head could be healed.

Check out my http://www.gamesas.com/bgsforums/index.php?showtopic=1039524 about this same thing, you might find your answer there.

I know Patchwork is always getting bits of himself reattached and that seems to work.