I fully support one-time change for character creating (name, race, gender, etc.) because many people might be now using their 2nd best choice only because what they actually want wasn't available at the time, like, say, male Miqo'te. Since they're adding new race/gender combinations, and the graphic is bound to change/alter, it would only be fair if existing players get to recreate their character as well.

Changing Grand Company and changing home nation don't sound as interesting for me.