I'd like to see a Plugin for manga like a manga viewer I don't really want a different app to manage my manga collection. Calibre needs this plugin! I'd also want it to separate the manga from the books/novels I wouldn't want them lumped in together.
Look at these to get an idea of what I'm thinking =)
MangaMeeya
http://www.mydailymanga.com/2008/06/...-reading-tool/
Honey View
http://www.honeyview.org/
CDisplay
http://www.cdisplay.me/