I'm sorta big into the fanfiction side of the fandom. I'm probably not the biggest authority on the subject, but I'd very much like to see a panel at the con for a discussion on a) fanfiction in the community, b) to discuss favorite authors or stories, and c) to maybe give some basics and tips on writing for ponyfics/general fanfics/writing in general. I know a good amount of the up-and-coming authors these days seem to cut their teeth writing fanfics (not just talking about that 50 Shades thing). It might be fun to talk about.
There's also an author over on FiMFiction.net - Wanderer D - who has made some fun 'How To'
post about writing on that site. Going through those might be cool as well (cleaning up the language where needed of course. ;P)
Oh, and if there were any way you could get some noted ponyfic authors to come and be a part of that that would be amazing.