Would it be possible to upgrade a stock ROM with an official update.zip when one receives it? If so please post it. 
As long as the file is signed by Motorola, wouldn't it be as simple as putting it on your sd card, booting into stock recovery, and picking that file or naming it properly so it is picked up automatically? Isn't that what an OTA update does?I don't think so. You'd have to have root to put the file in the proper place in your filesystem. I don't think it would flash from the SD card without doing the rigmarole we've been doing anyway.