So it'd be like MvC2?
The King of Fighters 2002 Unlimited Match is also another contender for largest roster (if you exclude boss characters but count in the alternate versions of Chris, Yashiro, Shermie, Kensou, Robert and Takuma), it features the characters that appeared between '99 and '02 (while TKoF 98 Ultimate Match featured the characters that appeared from '94 to '98. KoF 98 UM is also notable on this subject, due to the amount of alternate versions of the playable characters -- 16 out of 43)
http://www.youtube.com/watch?v=1E0kl5Wu0gI(I've seen Samurai Shodown VI sometimes, which must have all characters from I to V, but I'm not familiar enough with it)
I am not really a pc98 fan or anything but something about the moon staff that Mima wields makes me think she could be a cool fighting game character. That and her lack of legs making floating be a big part of her fighting game charm.
she could have Orreries Sun as her normal move (and/or Yuka could have the original Spark/Double Spark as her normal move too), but in a less powerful version (while having a "super" version of these moves as well). Think of it as Real Bout Fatal Fury's Chon Shu's drain life super move, against Chon Rei's drain life special move. (sometimes it feels weird that Chon Shu's super move and Chon Rei's negate each other).
She could also have a super where she changes into her HRtP form and stabs her opponent (I haven't thought of the functionality of that super, though), since we're speaking about weapons, or she could temporarily change "styles" and turn into her HRtP form and have different moves.
Regarding her flight ability, she could move quite slowly, as a reference to PoDD, and dash/fly quite fast, as a reference to MS, have ghost familiars (from MS) and a forward charge move like her (useless) thrust from SoEW.
She wouldn't fall when she jumps into the air 
Instead, she'd have to 'fly' herself back down. Unending aerial combos, commence!
Ha, that'd be neato. And the Sun and Moon staff would be awesome, too.
http://www.youtube.com/watch?v=UqmxhEfim3M :p
