I think it's safe to say that if therapists struggle for years to transform people, we're not going to succeed in helping players expunge deep-seated emotional dysfunctions during the course of a game.
However, if we narrow the scope of our goals, there's a lot we can do. After all, on some level, don't we vicariously experience the emotional growth of those characters in films with whom we identify? And haven't all of us been affected, if not changed, by one of those experiences?
After experiencing films with characters who go through change and identifying with those characters, are we ourselves actually changed? For instance:
Well, hopefully, we're changed at least a bit. If these films don't encourage us or even motivate us to change, even a little, then a lot of screenwriters, directors, actors, and other talent have spent great amounts of effort in vain.
If our goal in games is no more or less ambitious than those of filmmakers, I think we can succeed.
Of course, we already have available to us the tools filmmakers use. We can create empathy for one or more characters (see Chapter 2.10, "NPC Rooting Interest Techniques"), and we can then have these characters undergo a Character Arc (see Chapter 2.9, "NPC Character Arc Techniques").
But we want to do more. We want the player himself or herself to undergo change directly not just by empathizing with an NPC who changes.