Wow...that is a lengthy discussion. I'll read through it in a bit. This is great bc the 1284 needs an ongoing discussion to keep it alive. The nice thing about it is that is breadboard-able, which is key for the open hardware community.
On another note, I saw that you posted about bikes. A group at Code for Philly just finished the Cycle Philly app http://www.cyclephilly.org/ (which can be used anywhere). I am now working with that group to link it with bluetooth to a 1284 board that reads pollution data and will get linked to a map. The goal is to empower bikers to seek out pollution (and ultimately avoid it). We may be able to use your board design to move the project faster to an SMD design (its currently DIP).
LMK if you are interested in testing out a proto.
Cheers!