Folks, I'm sorry to report that I've hit the wall with analyzing those EFS dumps. I had hoped that I could eliminate the device-specific files by comparing the two non-Play-Store images uploaded, and that there remaining differences between those two images and the Play-Store image would be small and easy to analyze.
Unfortunately, there are just too many such differences to begin to figure out which ones might be relevant. Also, the recent discovery that Play Store devices do not erase as expected with adb erase commands makes me wonder if this difference is lower-level, like in hardware, nvram, or fuses.
I'm going to throw in the towel on the efs approach for now, and devote my hacking time to other protects like my app or flashing Jelly Bean.
If any of us has any new ideas, either of other data to analyze or of a better way to analyze efs data, I'd be happy to try hacking on this some more.
Anyone have access to bootloader source code? :P
Sent from my BANNED Unified-Search-enabled Galaxy Nexus.