This is a great idea for a panel. Actually when Jeni, Taco & Roget & I were out the other day we were talking about the individual ladies who comprise CLAMP themselves, and the unusual circumstances under which they comprise their work, the mythos about them, their individual quirks. That would be entertaining to hear more about. It would also be of interest to convey the impact they've had not only on artistry, but on the impression of what women can do, both as protagonists and as producers in the art form. You could also reference their reliance on intertextuality and how they have taken crossover to a whole new (and many would say crack) level. Also of note is the vast range of emotions evoked by their material, from the lightest fluff to the darkest despair, and what visual cues they use to accentuate the moods presented via their plots. Then some of the stuff you used to mention when you were on the Religion in Anime & Manga panel with me & Jeni & Guy would be worth including, at least showing the stuff from the art books you used to bring.
Moreover, it's worth tying in the local angle, that they use Copic ink pens & markers for their work, the sole U.S. distributor of which is located in Eugene.
Anyway, how much time were you allocating to the panel? I would think an hour if you are just talking, but at least 1.5 if you start actually showing clips.