Old topic,although I believe it is ok to post in it as long as it is still open and without warnings.
Actually, I think that Okuu counts more as a "sun themed" character than a "fire themed" one. As for Mokou, you could simply have her burst into flames and stuff, and even give her a trick that lets her explode and then reform almost immediately. That could work, maybe?
A little correction:Okuu is conceived by Zun more as a recipient for the "Ultimate Energy" aka an advanced form of nuclear fusion,so it is regarded more as a dual "nuclear and radiations-sun themed" character than as a pure "sun and sunlight themed" like Amaterasu is.
As for Mokou,it might work out as a basis.
However,thinking deeply about this one, there are sprites and animations which would overlap with Mokou's eventual fire and reforming moves;on top of my head I recall Remilia's and a bit of Marisa's during all fighters and Utsuho in HTS ,especially Story mode for Remi and Okuu, but there might be more in HM .
An additional loss of value would be the absence of Mokou -Kaguya 'cause the latter "Manipulation of Eternity" requires too much work to be both balanced and enjoyable and so another character pulls ahead replacing her,which might be for the better as they both need comprehension and polishing to not come out half-baked.
Brainstorming aside,
http://youtu.be/WWaLxFIVX1s is my reaction to missing out on voting on a new and unexpected Touhou Poll.Nice addition on the partner thing!
Well,it really shows the
hype for HM boosted quite a lot of faces in the Single Character popularity poll*looks at Koishi*! In spite of that,the Music and Partner polls are minimally affected and IMHO less hype-influenced.