I guess my viewpoint on the matter is a little warped since I've been stuck in college for 5 years and now just have a job and some extra money to spend on travels, etc, but I'll give my opinion anyways.
1. This year I'm not too thrilled with the headliner. Their back-catalog doesn't thrill me and I would rather see Redemption play. However, the quantity of amazing support bands is what got me going. Booking the not-so-headliner-ish bands are often a plus if they haven't toured in the US that much. Last year at BARFest, it was the first time Darkwater and Sun Caged played here, and they were amazing. I know ProgPower does that too, so I think that really helps.
2. If you can't get any retired bands to reform and headline a show, perhaps a band that hasn't gone on tour in a while would do. I know things are changing in the next year, but having a band like Nevermore or Tool, that haven't put out an album or done an extensive tour in a number of years, might get tons of fans (I don't really know how this forum really feels about tool to begin with). But you get the idea.
3. As someone mentioned earlier, it'd be cool to have a band on tour stop by and do a pre-announced special show / setlist. For example, Dream Theater could play the entire 6 degrees of inner turbulence or get Ayreon to somehow play something with their guest singers (Maynard did something like that with his Puscifer project).
4. This is my personal favorite idea, but I know it'll never fly
. Changethe festival to "ProgDeath USA" and book Gojira, Cynic and Opeth!! I mean, if you really want to sell out fast, thats how to do it. And make Opeth play Black Rose Immortal, that would get lots of people to come.
In any case, good luck and I hope the festival makes it through this rough time. Or tell Obama to give ProgPower a stimulus package. If the car companies can, so can we!