technically you already can change name. It's just an expensive procedure:

1: Move your character to another server.
2: Create a character on your original server with the same name as your main character.
3: Move your main character back to your original server. Name change prompt will then occur because your alt has taken your original character's name slot.
4: Delete the alt.

Though I guess this cannot be done if you have the subscription plan that limits you to one character per server :/