I have to agree with the OP. While I may not feel so strongly about the Legacy names to quit my server if I wanted to change, I think we should still be given the option.
I'm surprised that in a game that focuses so much on your personal storyline that they would force you to have the same surname across all characters on that server. Granted, surnames are not exactly game changing at all but if I want to be Lord Salad Tosser and Cipher Agent Kenny Rogers on the same server, I should have that option because that's who my character is.
I'm hoping we see an option to change legacy names once they flesh it all out.