This is an awesome idea but the longjam part is bumming me out. I'm not sure I could get myself and my programmer buddy/game jam partner-in-crime to devote two weeks worth of our time to it, given our schedules. 48 hours, though much more limited in scope, is a lot easier to manage.
But that might be going against what you're trying accomplish with this jam so feel free to take my words and toss them in the bin. :D Regardless, this sounds rad and hopefully I can find a way to get in.
Might also be worth linking to PixelProspector's Make Games site. It's filled with a TON of links and resources for engines, audio, and graphics help.
It's already linked on PP's site but I HELLA recommend BFXR for making sound effects. Super quick, easy, and fun to use.