I really am liking AuxLV's idea of an on device app that automatically produces a flashable zip! And I hope that even if this patch that I have attached does work that you will continue to pursue that end. Also feel free to use the attached files if they will help you! The main problem with the method that I am using is that I have to download the original rom zip for every single rom that I want to produce a patch for. Your method would be so much simpler and user friendly.
Ok, that said...
Here is the patch I produced using this rom: cm-10.1-20130219-NIGHTLY-grouper.zip. I don't know if it will work on other variants of the device(3g) but if it is shown to work on grouper I could produce the same for other devices.
THE ATTACHED ZIPS HAVE NOT BEEN TESTED AT ALL. I DON'T OWN A NEXUS 7 . FLASH AT YOUR OWN RISK
... And make a backup first!!!
On my tab2 I had to boot into a clean CM install once, then reboot to recovery and flash the patch with CWM.
The second attached zip will restore all your normal files / Phablet. Feel free to link to this but please no mirrors at this point.
I await feedback, I have subscribed to this thread.
Sent from my Nexus 7 using xda premium