Looks like a great project!  Ping me if you don't get a good response, but I expect you will.  I'd love to jump in but just launched some stuff of my own and I am bandwidth limited.

If you're using avr as your front end, why not flash it to arduino and do the firmware simply.  It's lame but what's the avr got to do?  Pass serial back and forth?  A bit of configuration on the front end, and after that it's grab bytes from USB and stuff into the fury.