I like the idea of a Masquerade with "hosts" like when the Ouran Host Club did it (I volunteered as an official host that night) and I think it would be really cool to have the Hetalia characters or any anime characters as hosting it since it IS an anime convention after all. People don't have to know the anime to enjoy the masquerade, you can even put a disclaimer like, "Don't know the hosts? That's okay, come enjoy dancing the night away anyway!" Or something in the pocket guide/program book ... It's not like the ball is centered around the anime that's hosting it. They'd just do a couple small gimmicks related to their anime to make it interesting to those who have seen the anime, but a gimmick where people can participate nonetheless if they know the anime or not... like finding Honey-Sempai's bunny and winning a dance. You didn't have to know the anime to find the bunny.
However if something is done like this though, or even hosts in general, there should be pre-con meetings to figure out what the hosts are going to do and dancing. That was the problem with the Ouran Hosts, is we only got to meet about an hour before the thing started to collaborate. Luckily we really only needed to learn the Waltz, pretty simple, the rest of the songs we just kind of danced to with others. Also the general hosts were kind of left out of the loop when it came to what stunts the main character hosts were going to pull. There should also be alot of pre-relations with convention staff. It was the first time it was done so we kept having to stop the dance to make announcements for staff, like about wearing shoes, fire codes, etc when all that should have been taken care of to begin with. And there were problems with some hosts getting down to the main events room before the event started as well, already cutting into the small practice time we had. I had to "argue" for a while with a Yoojimbo that I was a volunteer for the dance and I needed to get past the line and down into the event room to practice. Finally someone came to my rescue and told them they were going down as well to help and just to let me by, luckily they were staff. xD In fact, I believe that was you Washougal_Otaku. xD