Very interesting!
Some questions:
Why install lighttp?Piratebox uses a python web server with droopy.What do you use for the uploads?
Have you ever noticed problems with the ad-hoc network on some linux machines with network-manager?
What do you use to stop the process?

PS:The custom kernel is required only for the nat rule,without the nat rule every address that doesn't need to be resolved with dns won't redirect to the piratebox.
PPS:I'm not David.