I dont know I dont think Mugen is Formal enough He might just crash it, but im planning on trying to go to all the dances (All I do is dance)"Everyday im shuffling"
I'll be there as Stocking. Her outfit is the only cosplay I have that would work nicely for it.
It will be interesting for my boyfriend is going as Zero from Code Geass
I am not sure if they are having it this year.
But short skimpy dresses for a ball, probably no.
I'd get your most formal characters to cosplay there, if you can.
The ball description requests at least semi-formal wear. I usually wear an anime costume, but I've also gone in business clothing, matching tie, and white gloves.