Those planning on doing some customizing of their Nexus 6P should be happy to hear that Google has posted the Android 6.0 Marshmallow Factory Image belonging to the Nexus 6P. This way, if something goes wrong while installing a custom ROM, you can flash the Factory Image and have Android 6.0 on your device once again.
There happens to be two Android 6.0 builds of the Factory Image, MDA89D and MDB08K. One theory is that of the two builds, one is for the Project Fi version of the Nexus 6P. The Google owned hybrid carrier now allows subscribers to use the Nexus 6P and Nexus 5X along with the Nexus 6. Both builds of the Factory Image should work on a non Project Fi phone.
Despite the posting of the Factory Image, there is one major issue that could make Nexus 6P users decide not to flash custom ROMs on the phone. Apparently, unlocking the bootloader on the device blows a QFuse which cannot be reset to the default setting if you decide to re-lock the bootloader.