Oh man. You tempt me. I plan to go but have no schedule in mind, so this might not be a bad idea for me to get involved with.
What do you need?
Not much, just people who can talk Touhou. As a panelist, you don't need to do much, mainly keep conversation going. I like panels to be free-flowing, so I don't really plan a strict agenda (usually a rough one that covers the topics I want to touch on).
For this panel, what I'm leaning towards as topics are: the games, the Gensokyo world (and characters), influence of Touhou, doujin work (spinoff games, manga, music).
You do need to sign up at anpanels.com, and it does help (I think) to post on the AN board.
Having an audience would be great too (since I think one of the criteria that a panel is judged on for inclusion in subsequent cons is audience size).