The thought of having to redo/refarm everything me and my partner did for getting our guild ship etc together is really not one I ever want to worry about. We duo got the ship up without anyone else helping and that was a massive time sink for us.
Losing all of (of even some of) my character names is another thing that's really upsetting. I've had the characters a long time, I have RP built around them and each one has a back story and everything to it. I really don't want to lose a character name because of server merges.
I would suggest what I have suggested before - link character names to account much like NWO did with having say... Manathayria@account (or something similar to Blizzard's Battlenet tags) so duplicate names are allowed, but things like friends, ignore etc are linked to account so if you ignore someone, they're not going to pop up on a second character for you. Mailing in that game just had you add in the @account as well so it's a little more complicated, but the @accounts were able to be hidden if you wanted in chat.