Lol, I am a lefty for writing and I always use right one for a mouse, weapon, wiimote, or photoshop. This would be a nice idea for us want to customize our character. I don't see why my left-handed one should be off-hand only and no it shouldn't be in the character creation either.

It's not that hard to do for the dev team though. Programmers can agree that it's too easy to change.