Really? You were one of the other Rious? Which one? There was me and then 2 female Rious.
Anyway, Millie sounds like a good choice, if only because she's really cute and Bonaparte is also awesome. If you have time to make the costume, you should be Millie.
I actually haven't started my Theo costume yet, but I plan to within a day or so. Luckily it's very easy. I really don't even know much about making costumes. The Riou one was my first ever and my friend actually made most of it for me. It was a learning experience...though one where I learned less than I should have.
Hopefully though I'll be able to learn enough in the next few months so I can do Hix for Katsucon as I plan(and make it mostly by myself!)
And then next Otakon I have insanely scary plans to do Hortez VII. We'll see if I follow through on that. He's a bit more naked then I'd like, but the costume is just so very cool.
Anyway, let me know what you decide to do for AnimeNext so I can hunt you down. Though I'm sure I'd find you anyway, what with it being much smaller than Otakon and me looking obsessively for any Suikoden cosplayers.