Long time since i did not check the forum, and i'm quite happy to see that you have done a good work on this device
Android N have a beta program, i started with it since preview 1. Device work quite well but N for nexus 6 does not have native rsap support...
So i come here and started with the rsapinstaller, here is the screenshot, got an error Connect to SIM :
I got the logcat while the installer is running, i checked space on system partition and it look ok.
Tell me if you have any idea about the problem and whet is need to check.
Else i will try to go back to older android version
Thanks a lot