It almost surely can't happen this year, but for the sake of the future, I would love for Sayo Yamamoto to appear as a guest.
She has directed Michiko e Hatchin (soon to appear on Toonami), Lupin III ~The Woman Called Fujiko Mine~, openings and endings for several shows, such as Rage of Bahamut: Genesis, and episodes of shows including Samurai Champloo and Texhnolyze. She's also a protégé of Shinichiro Watanabe. Sayo Yamamoto is an interesting and exiting talent whom I'd love to get a chance to see at Otakon.
While I'm at it, I'd also love to see Rie Matsumoto be a guest. She direct