This might sound crazy, but I would unlock the bootloader (remember, that will erase your phone) and leave it unlocked. Then as new images (updates) are released, load them yourself. Yeah, I know, leaving the bootloader unlocked is a security issue if you're phone gets stolen, but it will make updating you phone much easier and you won't have to worry about erasing data every time you unlock. Also, on the N6, every time you LOCK the bootloader, it will erase your phone as well.
I used to ALWAYS re-lock my bootloader after every manual update I did, but it was just such a PITA to do that every time that now I just leave mine unlocked.